Final Flashcards
The shape of teeth tells us…
something about the animals ate and how they process their food-can help you infer what they ate, their diet-digestion, breaking down nutrients
2 parts of digestion
-physical digestion (mostly teeth-but for some dinos not at much) and chemical digestion (in the stomach)
Dinosaurs (and other groups) have a ___ dentition
thecodont dentition
thecodont dentition
teeth set in sockets -means that their tooth has a root that’s in a socket in the jawbone-like our teeth-all archosaurs have that
most vertebrates are ____ (in relation to dentition)
homodont
homodont
- means teeth same shape throughout jaw
- almost all animals have this characteristic
- so are (most) dinos
most mammals are _____ (in relation to dentition)
heterodont
heterodont
- different shaped teeth throughout your mouth
- canines-front teeth to cut, molars and premolars-can be blades or flat
heterodontosaurus
- whole group of dinos that are heterodonts
- means the organisms can eat a variety of diff food-diff tooth shapes allow them to process diff kinds of food
2 types of tooth replacement:
Polyphyodont, Diphyodont
Polyphyodont
(generations of teeth-fish-amphibians, reptiles)
-tooth replacement continues throughout life (replace teeth throughout life-constantly losing teeth and getting new ones)
Diphyodont
(mammals)
-only 2 generations of teeth-like humans-baby teeth then adult teeth, if get adult teeth removed then no new teeth will grow in
dinos were ____
polyphyodonts
One the adaptations for better chewing in mammals (polyphyodonts or diphyodonts?):
being Diphyodonts-they have only two sets of teeth, juvenile and adult.
- usually have fewer baby teeth and more adult teeth
- all mammals do this-have 2 generations of teeth
- having these 2 generations of teeth means once adult teeth come in, the top and bottom teeth will always be the same teeth touching each other-means top and bottom teeth fit together like a little puzzle-precise occlusion
- This allows for precise occlusion
precise occlusion
-the bringing of opposing surfaces of the teeth of the two jaws into contact, i.e. when lower teeth meet upper teeth as the mouth is closed
Diphyodonty and heterodonty allowed for…
…chewing in mammals. This was a key adaptation for processing plant matter
chewing is pretty ___ in the tetrapod world
- unique
- most animals don’t chew-most animals take big hunk of meat off and swallow it
- mammals chew-most animals don’t
- allows for processing plant matter
Plant matter is ___
- tough
- The cuticle on leaves is hard to break down
- Also, grasses may have lots of grit
- AND leaves are nutritionally poor, so you have to eat a lot of them…
how do mammals solve this (plants being tough to digest/nutritionally poor)?
-Mammals solve this with hypsodonty (tall teeth) -need to grind up plant material a lot-covered in dirt-will wear down teeth a lot-so long teeth so have time that even if wear down will still have teeth-also grinding will give them ridges, helpful in more grinding
so, herbivore teeth tended to be ____
- tall, and relatively flat with lots of ridges
- lots of ridges-scrape against each other, that’s how they grind up plants
- elephants do this, so do rats
dinosaurs couldn’t chew like mammals cuz didn’t have those grinding teeth-so how did they process plant material? Sauropods:
have gastroliths -basically they swallow rocks, have area in gut that’s muscular-plant material came into stomach with rocks, squeeze it all together to break down plant material using the rocks and grit
dinosaurs couldn’t chew like mammals cuz didn’t have those grinding teeth-so how did they process plant material? Thyreophorans and ceratopsians
gut fermentation -swallowed plants whole and let them rot in their guts-once they start to rot, releases some of the nutrients and able to get nutrients after plant has broken down over natural process of plants breaking down over time-some primates did this too
dinosaurs couldn’t chew like mammals cuz didn’t have those grinding teeth-so how did they process plant material? Hadrosaurs and Ceratopsians:
dental batteries
Dental Batteries
- some groups found a way around this Polyphyodont thing to find a way to chew-not like mammals do but found a unique way to chew-developed these things called dental batteries-basically a line of teeth-growing from the bottom up-older teeth at the top-at the top do the grinding-conveyor belt of teeth (works cuz constantly growing new teeth)-teeth constantly growing, grinding them down at the top
- Hadrosaurs and Ceratopsians
dinosaurs couldn’t chew like mammals cuz didn’t have those grinding teeth-so how did they process plant material? hadrosaurs:
cranial kinesis
cranial kinesis in hadrosaurs
-hadrosaurs developed whole new way to chew-mammals can chow cuz can move jaws from side to side-dinos couldn’t do this motion allowed by your lower jaw-took advantage of their cranial kinesis-our only joint is at jaw-dinos have kinetic skulls so all kinds of joints up in head-as the lower teeth come up, hit upper teeth and push them out, then there’s a little point so cheeks at the top flap out-that motions causes grinding-so when chew, not side to side, but cheeks going in and out as chew
ornithiscians had a ____
predentary bone
predentary bone in ornithiscians
-basically had little beak for helping tear off things and bring into mouth-nip off plant material and pull into mouth-nail like keratin material in front of mouth instead of teeth-modern horned mammal has this and looks like some dinos had it too
Dinosaur cheeks
- need cheeks to chew-food will spill out of mouth without cheeks
- so dinos that chew probably had cheeks, while carnivore dinos probably didn’t-no cheeks-cuz no processing in mouth-doesn’t need cheeks-just swallow whole
Eating meat is ____ (easy/hard)
- easy
- Just tear off a chunk and swallow
- Meat is relatively easy to digest-got lots of enzymes that can break down meat easily
- Requires blade-like teeth for tearing & cutting flesh
- Also, simple conical teeth for puncturing/ killing
T rex had ____ teeth (big/small)
T rex had giant teeth-probably for just killing, didn’t do much chewing-probably didn’t even do much tearing with teeth-just yanking into mouth then swallow whole
cats cup up food with ____
- side of jaw
- raspy tongue cleans meat from bone
- kill with front teeth, blade like teeth in back fro cutting up chunks to eat
mammals tend to have more ___ teeth for ____
- slicing, cutting
- cuz don’t swallow things whole-not doing much chewing though if carnivore
Tooth Serrations
Tooth Serrations
- Serrations help hold what is being cut in place
- Also help with keeping the edge sharp
- Can also hold bacteria only some groups-some debate about it (e.g., Komodo dragon)
- theropod teeth serrated
skull and lower jaw also hold clues to feeding in mammals-hyena vs rabbit jaw
- hyena jaw more scissor like, good for tearing-like sideways V
- rabbit jaw-2 Ls on their backs, connect at bottom of L-having jaw above the tooth bone-allowed teeth to meet at same time-good for grinding
masseters
- in herbivores, like warthogs
- allow to do side to side motion-emphasize those muscles so can do side to side grinding
a warthog is a plant eater-so why are there giant teeth at the front?
- this is where things get complicated-sometimes see herbivores with big pointy teeth
- usually when see in herbivores-some kind of sexual selection-male warthog, uses big teeth to show how sexy is, attract mates
Dino jaw shape
- same thing as before, first type of jaw (seen in T rex) is good for meat eating (like V)
- second one (2 Ls-but now like lying on so small part of L faces down on left side-so joint below bend)-herbivores-instead of jaw bone being above tooth growth, it’s below-but effect is the same-teeth will meet at the same time to do grinding
Specialized Teeth - Piscivores
- Fish-eaters tend to have long, thin snouts with homodont, pointed teeth for catching fast fish-fish are really fast so need jaw that will close really fast and has little tiny teeth to grab onto them
- long snout
- some dinos were probably piscivores as well-ate fish
Spinosaurs and Pterosaurs
- think ate fish cuz adaptations/characteristics similar to others that did
- pterosaurs-not dinos but closely related
- some specialized dinos needed specialized teeth-other types of specialized teeth or having no teeth-these are just examples of how teeth can show diet and how ate
Dinosaur Physiology
- meaning how got energy, what did they use it for
- Cold-blooded vs. Warm-blooded Dinosaurs-this is argued-most say somewhat warm-blooded, but neither of these terms are very good-better terms to describe it, also this is too dichotic-2 poles-many animals, like dinos, are more in the middle
Types of Metabolism
- Endotherms – generate heat internally
- Ectotherms – need external sources of heat
- Homeotherms – maintain constant internal body temperature
- Poikilotherms – body temperature varies, usually in relation to the environment-goes up and down depending on what’s going on in environment
- (most) Mammals and Birds – endothermic homeotherms-generate heat internally, use to keep relatively constant body temperature
- (most) modern “reptiles” – ectothermic poikilotherms
Endotherms
generate heat internally
Ectotherms
need external sources of heat
Homeotherms
maintain constant internal body temperature
Poikilotherms
body temperature varies, usually in relation to the environment-goes up and down depending on what’s going on in environment
endothermic homeotherms
- (most) Mammals and Birds-but also some fish and insects (exception)-and bats + some bird endothermic poikilotherms (exception)
- generate heat internally, use to keep relatively constant body temperature
ectothermic poikilotherms
- (most) modern “reptiles”-except some large reptiles (exception), which are ectothermic homeotherms
- most fish, amphibians, reptiles, and most invertebrates-body changes due to environment, external sources of heat from environment
Exceptions prove the rule…
- Bats and some birds endothermic poikilotherms (also hibernating mammals)
- Some fish and insects endothermic homeotherms
- Some large reptiles ectothermic homeotherms
which is better? endothermy or ectothermy? or poikilotherms? or homeotherms?
No way is better than another-all about tradeoffs, each has own benefits and costs
Endothermy benefits
– Sustained activity
– Active at night
– Adaptation to cold environments
Endothermy costs
– Requires LOTS of food - 10-30x similarly sized ectotherms
– Not efficient at small body sizes…why? (has to do with surface area/volume ratio)
Ectothermy benefits?
– Adaptation to hot environments
– Need little food
Ectothermy costs
(primitive condition-but that’s okay)
– Capable of only short bursts of activity
– Limited ability to be active at night
why is endothermy not efficient for small body sizes? SA/
-Surface Area/Volume relationship
Surface area/volume relationship
- if small, most of matter is closer to the surface-less volume relative to surface area-high surface area to volume ratio
- if bigger, stuff in middle that’s farther from the edges/outside-a lot more volume relative to the surface area-low surface area to volume ratio
- so larger animals tend to have a lower SA:V ratio/low SA compared to volume compared to that of smaller animals
why is this SA:V ratio important?
-The surface area of an animal is where it exchanges heat with the environment-small endotherms have a problem retaining heat cuz high SA to V ratio-big endotherms have problems dumping heat-may overheat-so big animals like elephants tend to have big radiators-like big ears on elephants-to increase SA
Small endotherms have a problem with ____
retaining heat (because they have high SA/V)
Large endotherms have a problem with ____
dumping excess heat (because they have low SA/V)
SO, mammals (endotherms) tend to be (in regards to size) ____
no smaller than a few inches
ectotherm size (can they be smaller than a few inches?)
-doesn’t matter if ectotherm-actually better to smaller-can get really tiny
Gigantothermy
- Large animals retain heat
- So large ectotherms can be homeothermic…
So what about dinos?
- If they were endotherms did they overheat?
- If they were ectotherms were they gigantotherms?
- what were dinosaurs?! Ectotherms? Gigantotherms? Endotherms?
- Were they all the same?!
- this is why there’s such big debate about dinosaur endo vs. ectothermy
- cladogram doesn’t really help here-ectotherms primitive trait-endothermy evolved somewhere-but we don’t know where-the 2 living groups that are on either side of the dinos-birds and crocs-are different-so that doesn’t really help us. Could mean endothermy evolved on before or after dinos
What lines of evidence can we use to solve this…? (if dinos were ectothermic/endothermic/etc.)
- Cardiopulmonary evidence – hearts & lungs
- Insulation
- Bone and growth rates
- Neurophysiology – relative brain size
- Isotopic evidence
- Skull features – turbinates
- Posture – bipedality & running
- Biogeographic Distribution – Do we find dinosaurs in cold places?
Cardiopulmonary evidence-hearts
-what’s interesting is that hole area-people think there may have been a heart there-think can even see chambers within the heart-know all modern endotherms have a 4 chambered heart-4 chambered heart tends to be much more efficient in terms of pumping oxygenated blood around-mammals and birds have a 4 chambered heart-but it turns out that doesn’t help us very much, cuz it turns out crocs also had a 4 chambered heart-so the fact that they found a 4 chambered heart in that dino isn’t that surprising-this bracket below tells us that dinos probably had a 4 chambered heart -now there’s some question about whether it’s the same 4 chambered heart in crocs and birds, whether it’s homologous, or if it’s an analagous thing-did they evolve them convergently or separately-some debate about this-turns out 4 chambered hearts in crocs are a little different and mostly used less because of their efficiency in pumping, more cuz of thier efficiency for diving, so crocs have a special shunt that they use in their blood supply and circulatory system when they’re diving to preserve oxygen and things like that-the point here is that the fact that finding the 4 chambered heart in this dino isn’t particularly surprising-it may hint that they are endotherms, but the fact that crocs have them tell us that this isn’t particularly conclusive
Cardiopulmonary evidence-lungs
Bird Lungs:
- Bird have a number of air sacs connecting to their respiratory pathway -basically just dead spaces of air-there isn’t oxygen exchange happening in them-that only happens in the lungs-but basically these air sacs that are connected to the respiratory sac that extend into parts of their skeleton and parts of their axial skeleton and things like that that kind of fill up their body-fill up their spaces with these air sacs
- This (these air sacs) allows for more efficient one-way airflow during breathing
- what happens is they breathe in, air goes into air sacs, no oxygen exchange happens, and then on the next breath that air moves across the lungs, and then on the next breath it gets moved out-takes them 2 full cycles of respiration to get air in and out-this allows for very efficient oxygen exchange when air goes across the lungs-in mammals, breathe air in, goes into lungs, sits there for a while doing nothing-in this case, the air is always moving through the lungs, and that actually allowed for more efficient oxygen exchange (called countercurrent flow)-birds need this-flying is costly in terms of oxygen-need oxygen to fuel muscles used for flying
- mammals and birds (endotherms) have high oxygen demands, birds even more so than mammals
- if were to see these kinds of air sacs in dinos, would imply there’s some sort of high oxygen demand
- It seems that some dinosaurs had air sacs too, similar to modern birds
- air sacs in sauropod vertebra-probably filled with air-a number of air sacs wrapped around vertebrae
- the fact that dinos had air sacs speaks to the fact that maybe they were endotherms, like birds and mammals are
endotherms tend to breathe ___ than ectotherms
- more
- have higher respiration rates-ectotherms like snakes don’t breathe as often-cuz metabolism relatively low-main reason breathe in oxygen is to help you break down food taking it-so cuz don’t eat that much food don’t need as much oxygen-mammals and birds on the other hand have high oxygen demands, birds even more so than mammals
and it seems crocodiles had ____ (in relation to breathing/lungs)
- have 1 way breathing too
- but don’t do it the same as birds-like the way their 4 chambered hearts aren’t the same as birds-do it slightly differently, has more to do with diving in crocodiles-so that tells us that maybe the air sacs in dinos weren’t for efficient breathing-this study is only a couple of years old-the fact that we’re just finding this out about crocs points out that there’s a lot of stuff out there about animals that we still don’t know-lots of work to still be done even about living animals
Insulation evidence
- Only modern endotherms have insulation (something to insulate their bodies)
- Birds have feathers
- Mammals have fur
- It seems that many dinosaurs had feathers too… maybe not as many as modern birds but just the fact that dinos had any insulation at all points to dinos being endotherms-cuz helps you keep in the heat that you’re generating
- we find more and more evidence for feathered dinos every year
Bone Growth evidence-human bones
- our bones are not solid-are hollow on the inside-solid part on the outside called compact bone-and then on the inside the bone is either hollow or has spongy looking bone-it’s within this space (in hollow part or holes in sponge) where you have marrow
- we’re gonna be looking more at the compact bone-the diff between endotherms and ectotherms of their compact outside area of bone
- most of bones in body start off with cartilage model-later gets replaced by bone, first shaft then ends-then growth plate between the shaft and ends of the bone-that’s how bones grow
- the growth plate is key-limits how big you can grow-so we have a determinate growth
- reptiles on the other hand have what’s called indeterminate growth
Bone Growth evidence-endotherms vs. ectotherms
-endotherms tend to have determinate growth and ectotherms tend to have indeterminate growth
determinate growth
-predetermined how tall we can be when born-nutrition can affect this but for the most part mammals and birds have determinate growth
indeterminate growth
growth happens in similar way, but no growth plan-body just keeps adding more and more bone on the outside of a bone, bone keeps getting bigger and bigger-reptile can grow indefinitely-growth rate slows down over time, but never stops
Bone Growth evidence-bone microstructure/compact bone (in mammals)
- the other thing we want to look at inside the bone is look at that compact bone in more detail
- compact bone actually isn’t solid, is only mostly solid-has some blood vessels running through it-because bone is a living material-it grows, it has cells that are constantly remodeling, it turns out 5-10 years from now all of your bone will be diff from the bone you have now, because slowly replaced with new bone-so it’s highly revascular, has lots of blood vessels-and it’s always being remodeled, reworked-reworking is often unorganized-if you look at it up close, see bulls-eye like structure, called osteon-in the middle of it is a blood vessel/where the blood vessels go called the haversian canal-and all the dark parts are where a bone cell lives (what’s called a osteocyte)-they’re constantly reworking bones-break down osteons, rebuild new osteons-constantly rebuilding that bulls-eye structure-and they don’t do it with a whole lot of organization-sometimes mammalian bone is called “woven” because it’s disorganized like this-with lots of layers all over each other and reworked
Bone Growth evidence-bird bone
- similar to mammalian bone
- same reworked, woven bone-not organized, random placement of osteocytes-tends to be relatively random
Bone Growth evidence-Lines of arrested growth (LAGs)
- another thing we see in bones, especially those of ecotherms
- definition: Characterize times of slowed/stopped growth
- ectotherms are constantly laying down bone on the outside so they can grow indeterminately-that growth doesn’t happen continuously-grows for a little, then stops for a while, then grows again, then sits for a while, etc.
- can see this stopping and starting in what are called lines of arrested growth
- tend to be on annual cycles-when it gets cold ectotherms, generate their heat internally, so they tend to stop growing because they can’t put their resources/energy into growing because they’re putting energy into staying warm-so they don’t grow in the winter months-then they grow when it gets warm out
- because lines of arrested growth have to do with changes in temperature, tend to be seen more in ectotherm
- Similar to tree rings-grow in spurts then stop-looking at them gives hint to past/climate of past
Bone Growth evidence-Dinosaur bones
- dinosaur bones, when you look at them in crossection, are often woven like bird and mammal bones, with disorganized growth-but, they also sometimes have LAGs, which speaks to some sort of arrested growth that’s going on-a little equivocal-bones that sometimes look like mammal and bird bones, but also sometimes like reptiles
- but there’s another twist to this story: it turns out that sometimes mammals get LAGs too-certain mammals, esp those who live in environments that are highly variable, often get these LAGs-usually looks random and woven but every once in a while get some LAGs-this is similar to dinos-so maybe the fact that dinos have these LAGs is not that big of deal, doesn’t say much about endothermy vs. ectothermy-so this bone growth stuff is a little unclear
BUT, it turns out…(in relation to LAGs/exception to rule)
some mammals get LAGs too
Growth Rate evidence-mammals and birds
- tend to have a 3 part growth curve:
- Slow growth as infants and toddlers
- Fast growth as juveniles and adolescents
- Slow growth (or stopping) as adults
Growth Rate evidence-ectotherms
-tend to have a relatively constant growth rate-does slow down as gets older but don’t have this 3 part growth curve
Growth Rate evidence-Dinosaur growth rates
- Dinos had a 3 part growth curve, especially the biggest ones
- They also grew at rates faster than birds or mammals-the large ones are putting on 10s of kg a day (during their time of highest growth rate)-literally 20 lbs a day-pretty extreme-the fact that they’re extreme is more similar to endotherms than ectotherms-some mammals do this, like whales
- Large sauropods: 20 kg/day (similar to whales)
- Large theropods: 2 kg/day (similar to birds & mammals)
- Small-mid-sized: 1-800 g/day
Growth Rate evidence-Dinosaur life spans
- Large sauropods: 50 yrs
- Large theropods: 30 yrs
- Small to mid-sized: 7-15 yrs
- Smallest: 3-4 yrs
Growth Rate evidence-Dinoaur growth rates and life spans in relation to ectotherms/endotherms
-All of this is similar to modern endotherms-pretty similar to modern mammals if scale them up to these sizes-the fact that dinosaur growth compared to life spans are similar speaks to this
Growth Rate evidence-Encephalization Quotient
- Ratio of brain size to body size
- brains are metabolically expensive, meaning that it takes a lot of energy and oxygen to keep brains going-so only animals with access to a lot of energy and oxygen have large brains
- one way we measure the size of brains is not absolute size, cuz then would say whale have bigger brains than humans-what we use is relative brain size-ratio of brain size to body size-called the encephalization quotient
endotherms have a ____ Encephalization Quotient
- high-because brains are expensive
- humans have a very big brain for their body size
Growth Rate evidence-Encephalization Quotient
- Dinosaurs show a range of encephalization quotient, with some similar to modern birds
- some really small brains-but some ornithopods and some meat-eating dinos have pretty big brains, similar to birds
Isotopes and Body Temperature evidence
- Different isotopes have different weights (Why?) has to do with the fact that they basically have diff number of neutrons-C 12 and C 14 act the same chemically cuz have the same number of protons-but have diff numbers of neutrons so C14 is heavier-neutrons don’t have anything to do with chemicals to C14 acts just like C12-could make CO2 out of C14, carbon in bodies out of it, and so on and so forth. It’s just a little heavier.
- Lighter isotopes are preferred in most chemical reactions though-it’s easier to move them around because they’re lighter-chemical reactions driven by heat, the heat tends to move things that are lighter rather than heavier-lighter tend to be more incorporated into chemical reactions
- At higher temperatures this difference between the 2 becomes less -at low temperatures the C12 is more preferred than the C14-but as get higher and higher temperature the difference between the 2 doesn’t matter as much -at higher temps, the diff of weight doesn’t matter as much, because there’s enough heat to move whatever you want around
- use this to tell relative body temps on species (temp at extremities vs. core)
Isotopes and Body Temperature evidence-what this means for ectothermy/endothermy
-Extremities on the body (e.g., limbs and tails) will be colder in ectotherms-lizards get very cold hands and feet-keep whatever heat they’ve got in their core-what this means is that there’s less of a diff in temperature between the core of an ectotherm, like you, and its fingertips-in an ectotherm, there’s a big diff in temp between these 2 places-this means basically the diff in isotope usage between the extremities won’t vary very much because the temperature’s pretty similar-but in ectotherms huge diff in isotope usage between core and extremities because extremities so much colder so harder to move heavier isotopes around
-large modern lizards (like kimodo dragon) tend to have bigger differences between tail/extremities and core than dinos-dino differences in temp between extremities and core more comparable to mammals
(this is all relative, not absolute temps)
Isotopes and Body Temperature evidence-large modern lizards
(like kimodo dragon) tend to have bigger differences between tail/extremities and core than dinos
Isotopes and Body Temperature evidence-dinos
dino differences in temp between extremities and core more comparable to mammals-not as large differences as lizards
Isotopes and Body Temperature evidence-Absolute Measures of Temperature
-Uses “clumping” of isotopes at different temperatures-when they do this and look at dinos to find abs temp-looks like dinos had relatively high body temps-similar to endotherms
Skull Features evidence
- Mammals and birds have unique structures in their nose, the turbinates that make their breathing more efficient -little bony structures in the nose, covered in epiphelium, covered in tissue, that makes a bunch of snot-it also has a lot of blood vessels in it
- what happens is, as the animal breathes in, cold air from outside goes across those turbinates that are covered in snot and picks up moisture and heat, and that in turn goes down to the lungs-lungs better at getting oxygen out of warm moist air-when mammals breathe, breathe a lot, high respiration rate,want to get as much oxygen as possible, so wanna do this is the most efficient way-this way gets more oxygen, is very efficient-helps maintain heat and moisture
- don’t want to lose all that moisture and heat, so what happens is when the air goes back out, that air dumps its heat and dump its moisture onto the turbinates, then just air is breathed out and it’s relatively cool-creature conserves that heat and moisture
- animals that run a lot (pursuit predators not pounce predators-chase their prey down) have more complex turbinates cuz need to be more efficient in breathing
Skull Features evidence-turbinates-what happens when breathe in
- what happens is, as the animal breathes in, cold air from outside goes across those turbinates that are covered in snot and picks up moisture and heat, and that in turn goes down to the lungs-lungs better at getting oxygen out of warm moist air-when mammals breathe, breathe a lot, high respiration rate,want to get as much oxygen as possible, so wanna do this is the most efficient way-this way gets more oxygen, is very efficient-helps maintain heat and moisture
- relatively cool, dry air passes over moist, warm turbinates and is heated and saturated with water
do humans have turbinates?
yes, except they’re pretty little one-3 on each side, look like little commas-not as cool and intricate as dino ones
Skull Features evidence-turbinates-what happens when breathe out
- don’t want to lose all that moisture and heat, so what happens is when the air goes back out, that air dumps its heat and dump its moisture onto the turbinates, then just air is breathed out and it’s relatively cool-creature conserves that heat and moisture
- warm, most air passes over cooler, drier turbinates and transfers heat and moisture to their surface
-animals that run a lot (pursuit predators not pounce predators-chase their prey down) have ____ turbinates
more complex turbinates, cuz need to be more efficient in breathing
Skull Features evidence-Function of Turbinates
1) Condition incoming air
2) Conserve heat
3) Conserve water
Because: High ventilation rates* in endotherms create a water and heat conservation problem
*Ventilation rate = breaths/minute
Skull Features evidence-Did dinosaurs have turbinates?
- Turbinates don’t fossilize well-tend to be broken in fossils-hard to find specimens that still have these specimens inside nose
- Use nasal volume (how big it is) as a proxy for how many turbines in it
- dinos fall on reptile line-so probably did not have turbinates, which is something we associate with endotherms-mammals have them, and birds do too, but cartilaginous (made of cartilage) in birds-ectotherms don’t have them-dinos don’t have them, except then new study
- study from about 5 years ago, actually think they did have turbinates-did same sort of CT scans across the nose-did some modeling-think dinos did have at least very simple sorts of turbinates-the evidence is a little unclear, just like everything else so far
Postural Evidence-lizards
- lizards are sprawled, arms out on sides-runs side to side
- lizards, when run, run side to side-air gets compressed, pushing air from 1 lung to another (expanding) moves from one side to the other-instead of air moving in and out of mouths, moving back and forth and side to side
- lizards, if chase them, eventually slow down, cuz used all their heat/energy-but also because can’t breathe well while running-can’t get oxygen in while they’re running
Postural Evidence-dinos
-have upright posture with their legs not on their sides but underneath them-legs run underneath body (like mammals)
Postural Evidence-mammals
- have upright posture with their legs not on their sides but underneath them-legs run underneath body-for 4 legged mammals
- upright posture allows mammals to time their breathing with their running
- mammals, with legs beneath them, can actually time breathing and moving legs/running together-mammal takes a big step forward, breathes in, then breathes out-can time this-expands chest, breathe in-compressed chest-then breathe out-can time those things together-remember mammals use a lot of oxygen-so if can use oxygen more efficiently, means can run longer distances, run more efficiently
- mammals can breathe while running-this has to do with this endothermy
Postural Evidence-crocodilians and mammal-like reptiles
-crocodilians and mammal-like reptiles somewhere in between, have semi-sprawling gait-you might expect that since midground between this and that-crocs a little weird, a little diff, peculiar
Postural Evidence-dinos, birds, and humans-why are they diff?
-dinos, birds, and humans are diff cuz they’re bipedal-moving just on hindlimbs-not doing this sort of thing
Postural Evidence-how this relates to dino endothermy/ectothermy?
- there still is a sort of timing of breathing to walking, even if only walking on 2 limbs-but a little diff
- the fact that dinos walk upright, have limbs beneath them, shows they’re more like endotherms than ectotherms
Biogeographic Evidence
- Dinosaurs did live near the poles-like Antarctica
- Modern ectotherms don’t-don’t tend to get ectotherms near the poles-can’t absorb enough heat
- BUT, the Mesozoic was a much warmer time
- so maybe the fact that they lived at poles doesn’t mean too much
- Maybe dinosaurs migrated-maybe what they did to avoid being too cold was just keep moving to the warmest places
- but still, the fact that we find dinos at the poles is pretty interesting-and looks like some dinos lived at the poles year round, didn’t migrate-even if it was a warmer time, this is just a colder area than the equator-shows that maybe dinos could handle the cold-this could speak towards endothermy
Biogeographic Evidence -isotopes
-basically can figure out temps by looking at isotopes-if look at isotopes across one tooth of dino, can estimate what temp living in-what graph shows is what map shows-looks like some dinos migrated, during summer go to mountains, then down to plains when colder-so they did some migration-modern mammals do this-so maybe what they did to avoid being too cold was just keep moving to the warmest places
TO SUM IT UP, ecology argues for endo or ecto?
- endo
- Dinosaurs have the same predator prey ratios as mammals-1 carnivore for every 10 herbivores in modern endothermic ecosystems-in ectothermic ecosystems, a little diff, don’t need as many herbivores to support a carnivore cuz their energy levels aren’t as high
TO SUM IT UP, cardiopulmonary evidence argues for endo or ecto?
- endo
- Dinosaurs have 4-chambered heart and lung air sacs like birds, and may have had one-way airflow-this evidence is a little bit equivocal cuz of crocodiles being a little peculiar, but still points to endothermy
TO SUM IT UP, Insulation evidence argues for endo or ecto?
- endo
- Dinosaurs had insulating feathers, like fur or bird feathers
TO SUM IT UP, Bone and Growth rates argue for endo or ecto?
- endo OR ecto
- Dinosaurs have bone characters like mammals/bird with complex growth, but also show LAGs-this is more equivocal-so endo or ecto-but tends more towards endo
TO SUM IT UP, Neurophysiological evidence argues for endo or ecto?
- ecto
- Most dinosaurs have small brains for their body size, although some are as large as birds/mammals -could probably argue endo or ecto
TO SUM IT UP, Isotopic evidence (diff between core and extremity temp) argues for endo or ecto?
- endo
- Dinosaurs have inferred temperatures like birds/mammals and little difference between core and extremities (also like birds/ mammals)
TO SUM IT UP, skull features argue for endo or ecto?
- endo or ecto
- Dinosaurs may have had turbinates like birds/mammals do-but unclear
TO SUM IT UP, posture argues for endo or ecto?
- endo
- Dinosaurs have non-sprawling posture like birds/mammals
TO SUM IT UP, Biogeographic Distribution evidence argues for endo or ecto?
- endo
- Dinosaurs lived in cold environments (poles and mountains) although may have migrated-but some didn’t
So which is it????!??! (are dinos endotherms or ectotherms?)
- a lot of this evidence is equivocal-evidence for both
- can we give a definitive answer?
- maybe we’re asking the wrong question-maybe dinos did something totally different
- that’s what’s why we’re getting such weird answers when we try to answer the question this way-basically that’s what the Goldilocks Hypothesis is all about
The “Goldilocks Hypothesis”
- Animals can put energy into two diff things: maintenance (renewing cells, generating heat, finding food) or production (growth, reproduction, fat storage)
- can put some of energy into maintenance (day to day life things) or could put energy into production (the extra stuff-getting bigger, having offspring, etc)
- ectotherms and endotherms apportion energy differently
- ectotherms: 60% on maintanance, 40% on production
- endotherms: 97% on maintenance, 3% on production
- remember, being an endotherm is costly-most of energy goes into maintenance cuz have to maintain energy levels, maintain internal heat-costly-so endothermy not necessarily the best strategy as we often believe
- ectotherms tend to be pretty even in spreading energy between maintenance and production-can spend more energy on growth than endotherms, that’s why they have indeterminate growth, unlike endotherms
- what the Goldilocks hypothesis is, is that it says dinos were somewhere in between-not endothermic or ectothermic-but mesothermic
Dinosaurs as mesotherms
- dinos somewhere in between endotherms and ectotherms-They had intermediate metabolic rates, but burned energy like ectotherms (i.e., put relatively more energy into production)
- So, they could more energy into growth
- Remember, dinosaurs got bigger over time (Cope’s Rule) and probably were gigantothermic (meaning that although they didn’t generate their heat internally, they had a relatively constant body temp, just because they were big)
- what’s driving this growth in size is the evolutionary arms race (Red Queen Hypothesis-prey get bigger so predators get bigger so prey gets bigger and so on)
- ectotherms put more energy into production but tend to have a smaller pool of energy to draw from-just cuz they’re eating less, getting less energy in general
- endotherms have a large energy pool but put little of it into production-most of it gets put into maintenance
- dinos were somewhere in middle-this is why its the Goldilocks hypothesis-large pool of energy, and put lots of it into production-burn energy like an ectotherm, but have an energy pool like an endotherm-basically what this means is that dinos were doing something totally different (from modern species)-we just don’t have many good models for it today -the way it’s sometimes described as they can raise their body temp but they don’t defend it
Different Strokes for Different folks-Ectotherms
can put more energy into production, but have a smaller pool of energy to draw from
Different Strokes for Different folks-Mesotherms
have a large pool of energy, and can put lots of it into production (<–just right)
Different Strokes for Different folks-endotherms
have a larger energy pool, but can put little of it into production, because their maintenance is so costly
Mesotherms
- Raise their body temperature, but don’t ‘defend it’ -put energy into maintenance and increasing body temp, and then they become gigantothermic, and then they don’t defend it, meaning they don’t use energy to maintain a high body temp
- one of the lines of evidence for this comes from growth rates-rate in the middle between endo and ectotherms (for mesotherms and dinos)
- dinos fall in middle ground here between ectotherms and endotherms
Mesotherms besides dinos
- turns out there;s a few animals that fall in between that have this mesothermic body heat thing (examples below)
- Modern examples: tuna, echidna, sea turtles
- tend to have this metabolic middle ground-between endotherms and ectotherms-and some modern species have this too but not many-maybe dinos were the only ones filling up this space for a while, back in the mesozoic
But there’s a breaking point…
-If you increase metabolic rate TOO much ….
- you become fully endothermic
- This may have happened to some lineages of theropods
- One line of evidence of this– they’re the main group to develop feathers -all dinos have some kind of featherlike structure but theropods do it to the extreme
- Also, some theropods become herbivorous – more energy at lower tropic levels, in plants
- And there are no giants in these lineages -so there’s lineages that lead to birds don’t get very big
- And some become birds…
- May also explain why there are no small dinosaurs (in other lineages) or marine dinosaurs (because they couldn’t do that without going over the line and becoming endothermic)
So the answer to our question (of dino endo vs ectothermy) is that dinos….
- were probably a mix of ecotherms and endotherms and many of them probably fell in between
- May have changed their metabolic as they grew-huge dinos start out really small-maybe were endothermic as younger, became ectothermic and gigantothermic as got older
- Some taxa were probably more to one end or the other…
- so “are dinos ecto or endothermic?” is not a good question
- there is no good answer
- the answer is that they’re somewhere in between-they’re in between
Charles Darwin
(not sure if need to know for final)
- Born in England, mother died when he was 8, father physician, out on house calls, raised by older sisters
- lived off his father’s money until he made him get a job
- went to Edinburgh University to become a doctor-fell in love with natural history-met some botanists and geologists-decided didn’t want to be a doctor
- trained to be a parson at Cambridge-a country priest-less formal than what we think of as priests now-priest that local people would go to, hold small services
- this was a good job for someone of his (high) class-something that kids had nothing to do, what they did-but while he was training, he got asked to go on a voyage on the Beagle as a naturalist (to keep captain company mostly, since captain was high class and didn’t want to socialize w low class sailors-and do some natural history stuff)-2nd choice, 1st couldn’t go-Beagle was a ship of the navy, travelled the world, map coastline of south america-important strategically cuz England had holdings there
- Darwin did a lot on the ship though-get off boat, hire guide, take a mule or horse and meet boat farther down coast cuz got seasick-made a lot of observations during this
- while on this trip got kinda famous-sending reports back to newspapers in England-when came back was pretty famous cuz he had a column, people reading it
- publishes book when he gets back, basically lives the rest of his life as an author
- marries cousin Emma-not uncommon at the time
Darwin Timeline
-1839-publishes first book, on the Beagle voyage
-also marries his first cousin, Emma Edgewood
-1840-develops his mysterious illness-people have debated what this illness was-due to stress about thinking of publishing his theory of evolution? tropical disease picked up on his trip? psychosomatic? he spent the rest of his life mostly at home sick
-1843 moves to Dorn house with Emma-lived the rest of their lives there-had 11 children, 2 died in infancy
-1851-daughter Annie (favorite, helped him with science stuff) dies-huge event in Darwin’s life-changed his outlook on life, probably views on religion
-1858-presents an abstract on the Origin of Species
-1859-publishes the full book-later goes through 6 editions
-does lots of work and publishing from home after this
1882-died-friends and supporters (esp Thomas Huxley) petitioned to have him buried in Westminster Abbey-buried with honor there
Darwin’s publications
- published 19 books
- talked about animals he found on his trip on the Beagle
- published 6 version of Origin of Species
- did not mention man in this book-but later published a book called the Descent of Man-more of his ideas on human evolution
- published books on biology, barnacles, animals, scientific inquiry, etc.
Theropods
- a diverse group of bipedal saurischian dinosaurs
- birds are actually the descendants of small nonflying theropods
- The most popular group of dinosaurs
- Both with the public and paleontologists – 40% of all dinosaur species named
- Most debated group in dinosaur studies
- Extremely diverse taxonomically and ecologically – But rare in the fossil record (10-20% of finds) -so amount found disproportionate to how many in ecosystem
- Widely distributed – present at every dinosaur fossil locality
theropods-herbivores or carnivores?
- Carnivores!!!
- Most are carnivorous with recurved, pointed teeth, some with serrations
- Characterized by intramandibular joint
theropod skulls-compact or no?
- Pneumatized Skull
- Lots of air spaces to lighten the skull
- Both between and within bones
- Seen in the post-cranial skeleton as well
- very small brain-most of the space in skull filled w air
- air sacs
- Similar to human sinuses-we have air sacs as well, called our sinuses
theropod brains
- Trend toward larger brains (in relation to body) -in some
- Some later taxa have EQs similar to birds
theropod senses
- Enhanced hearing and smell
- Stereoscopic Vision
theropod senses-Stereoscopic Vision
-when look T rex head on-eyes pointing towards you-means field of view of the 2 eyes cross over each other-gives depth perception (=the diff in position between your 2 eyes that tells you position)-many predators have this cuz helps catch prey-prey usually has eyes more on sides, so get wide range of vision to detect prey
theropods- bipedal or 4 legs?
Bipedal
- small and bipedal-many dinos evolved to walk on 4 legs later-but these guys stuck w 2 legs
- Only group to retain full obligate bipedality
- Much longer hindlimbs than forelimbs *
- Digitigrade *
- Reduction in digits I & V *
- 5 sacral vertebrae *
- Stiffened tails *
- =Running (Cursoriality)
theropods-Forelimb Characters
- Loss/reduction of digits IV & V as all dinos do(and sometimes III)
- Some opposability of digit I -can kind of grasp
- some dinos had really short arms-but short limbs were still strong! may have been used for something diff-to hold down prey? mating? unclear-but although small, weren’t weak
Theropod size
Huge Diversity in Size
- Tyrannosaurus rex (6000kg) to Mircoraptor (1kg)
- If you include modern birds the difference from smallest (hummingbird) to largest is 5,000,000x !
- largest terrestrial carnivore today is the polar bear, which is 10x smaller than T Rex
- T. rex largest terrestrial carnivore to have ever lived! in terms of mass
- Other theropods may have been taller than T. rex, but none heavier (probably)
- but not all theropods were big
were theropods the only predators around?
- other things around that weren’t theropods that were eating meat-more of them than theropods-and even out of theropods, most of them were small theropods
- dryadissector=another small predator that was common
Herrarasaurids
- South American
- Mid-Late Triassic (230Ma)
- Possibly basal theropods
- Possibly basal dinosaurs
- Defined by lack of characters
Coelophysids
- Mainly small, North American & African forms
- Late Triassic and Jurassic
- Coelophysis-most numerous dinosaur fossil
- Ghost Ranch Site, NM - all traveling in herd, killed in flood, lots of fossils in one area-La Brea tar pits?
were Coelophysids cannibals?
bones in animals found of some small organisms-originally thought these were bones of small Coelophysids -so were cannibals, older eating the young-some species do this, territorial thing, take over pack and eat young so know any future young are its own-maybe the case here-but now found that probably weren’t cannibals, were eating some other small animals
Abelisaurs
-Primarily Gondwanan – S.Amer, Africa, Madagascar, India, maybe Europe – Biogeographic implications -Mostly Cretaceous -Some have “headgear”
Ceratosaurs
- Horned dinosaurs
- Mainly Gondwanan
- Mainly Cretaceous
Tetanurae
- name means “Stiff Tail”
- Further reduced digits
- Loss of IV & V (as all dinos) and III reduced/lost (diff from other dinos)
- More pneumatized heads-extra skull hole-in front of antorbital fenestra
- Pubic foot
- Muscle attachment for muscles that move the tail
Spinosaurs
- Mainly Cretaceous
- Large, but lightly built
- Some have sail-backs – Why?
- Some piscivorous (long thin snouts with lots of little teeth-to catch fish)& semiaquatic (spent some time in the water
- Includes Megalosaurus
- long thin snouts with lots of little teeth
- Recent finds of a more complete skeleton
- Some now think they were semi-aquatic -thicker ribs-use to help them sink in the water-these guys had some ribs that looked similar to that-seen in modern animals like manatees-this is debated
What were the spines in Spinosaurs
used for?
- Thermoregulation?-maybe these guys were still ectothermic
- Cooling?
- Heat storage? like backpack to store heat and fat
- Cooling?
- Display? maybe colorful to attract mates
- Support? tendon that runs all along spine and to head-helps hold head up-patterns along spine like that make easier to hold head up, with the help of the tendon
Ratio of spine head to vertebral body size in dinos
-Dinosaurs more similar to mammals with humps for fat or support than to sail-backed mammal-like reptiles
Allosaurs
- Middle Jurassic to late Cretaceous
- Laurasian
- Some atain large sizes, but most are medium sized
Cleveland-Lloyd Dinosaur Quarry
-Central UT
-Species Counts:
– 44 Allosaurus
– 6 other theropods
– 9 sauropods
– 5 ornithopods
– 4 Stegosaurus
-Predator Trap! Locality was in sticky mud near a river bank-know cuz 10x more carnivorous than herbivores (looking at species found above)-should be other way around because of 10% energy transfer up pyramid-we talked about this before-prey got stuck, predators thought easy catch, went in and got caught too, kept happening
Coelosaurs
-Many convergent on earlier Allosaurs and Ceratosaurs
-Characterized by:
– Arctometararsals- metatarsals wrap around each other and are interlocked
– Semilunate carpal - relates to their ancestry to birds-relates to how birds come out of this group
Compsognathus
- Late Jurassic of Europe
- Near-shore islands
- “Turkey-sized”
- Probably feathered
Tyrannosaurs
- Late Cretaceous of Asia and North America, possibly also Australia
- Further digit loss – Arm use?
- Robust skulls-thick-restist hard forces, protect
- Dilong – feathered Tyrannosaur
- lots of variation in size-much more diversity in this group that people think! Cuz people usually just think of T rex
Ornithomimosaurs
- Cretaceous of Laurasia – Possibly also Gondwana
- many become omnivorous & herbivorous -so not all theropods are carnivorous!
- Some have bizarre osteological adaptations – E.g., Duck-like beaks
Alvarezsaurids
- Cretaceous of S. & N. America and Asia
- Short, stout forelimbs, with reduced digits-wrist bones fused together, then one huge finger
- would use stout fingers to dig up social insects-ants and termites-poke at them and pull out parts-maybe these guys were the anteaters of the Cretaceous
- didn’t have much in terms of teeth
Maniraptors
-Characters:
– Breast bones present in some
– In some the pubis faces backward like birds (and ornithischians)
-Possibly primitively omnivorous
-small
-may have evolved flight independently from birds-and in diff way-some had wings on front limb and hindlimb-gliders?
-some debate on their relationship to birds-do birds come from this group, or are they a separate group altogether?
microraptor gui
smallest dinosaur!
Oviraptors
- Late Cretaceous of Asia and N. America
- Misidentification of eggs gave them their name-originally thought were stealing eggs, but later realized were sitting on own eggs
- Similar to Ornithomimosaurs
- reinforced toothless jaws make have been used for crushing hard objects, e.g., clams
Therizinosaurs
-hyper-specialized giant forelimbs
-huge gut-digested plants in there, didn’t grind up in mouth
-Possibly analogous to giant ground sloths
-Cretaceous Laurasian in distribution
– Falcarius – from N. Amer. Oldest member of the group
Deinonychosauria
- “Terrible claw”
- Late Jurassic to Cretaceous
- Some possibly arboreal
- Some possibly omnivorous
- Group that birds are derived from
Overview -Triassic dinos:
Coelophysids and Herrarasaurids
Overview: Jurassic Dinos
– Laurasia
Allosaurs, Compsognathus, Deinonychosaurs
Gondwana
-Abelisaurs, Ceratosaurs
Overview: crestaceous dinos
Laurasia:
-Spinosaurs, Allosaurs, Tyrannosaurs, Ornithomimosaurs, Alvarezsaurids, Oviraptors, Therizinosaurs, Deinonychosaurs
Gondwana:
-Abelisaurs, Ceratorsaurs, Spinosaurs, Ornithomimosaurs (?) Alvarezsaurids (S.A.), Tyrannosaurs (?)
-increase in diversity in taxa and ecological groups, land changing, dividing
Evolution of large theropods (within ceratosaurs, allosaurs, tyrannosaurids) shows:
1) Increase in head size
2) Increase in tooth size.
3) Increase in jaw muscle mass (deeper jaw, larger adductor chamber.)
4) Greater skull rigidity.
5) Reduction in distal elongation.
Allosaurus vs tyrannosaurid killing techniques
Whereas Allosaurus may have killed by repeatedly applying relatively weak slashing bites and backing off (killed over time), large tyrannosaurids used more forceful crushing bites-nipping strategy (to get strips of flesh in tight spots) and “puncture and pull” biting
- like cats (tigers) and (wild) dogs today
- Dogs tend to attack in packs with many small nipping bites that wear down (large) prey (okay that it’s large cuz hunt in packs)
- Cats tend to be solitary, and kill with powerful “killing bites” and use their limbs
T Rex bite model
-nipping strategy )to get strips of flesh in tight spots) and “puncture and pull” biting
2-5 metric ton T.rex probably killed ____ and _____
ceratopsians and ankylosaurs (3.5-8 tons)
T rex ____ prey, didn’t _____
crush, didn’t nip
The Large Carnivore Macroevolutionary Ratchet
- Pervasive selection for large body size leads to the evolution of hypercarnivory (a diet of large prey)
- And this in turn leads to increased vulnerability to extinction.
- so as get bigger, eat larger prey-can’t live off little prey anymore cuz can’t get enough of them fast enough-and as get bigger, tend to get smaller population sizes, so more prone to extinction
- IF you are carnivorous, and selection favors larger size, THEN ….. energetic constraints will favor adaptations for taking large prey, and ….
- These specializations for hypercarnivory and large body size will result in reduced population densities, and vulnerability to extinction.
- Evolution of large size and dental specialization leads to a decline in evolutionary versatility (the ability to adapt to new conditions).
- EVOLUTION IS NOT PRESCIENT!
Advantages of size increase?
1) Predator avoidance-top of food chain, stronger, less predators after you and can defend self well
2) Can kill wider range of prey species.
3) Improved thermal efficiency.
4) Advantageous in interference competition-if you kill something, you get to eat all of it-don’t have to take a piece and run-no one will fight you for it/kick you out-Intraguild predation and carcass theft are significant among big predators. Body size often determines the winner.
theropods certainly ate ____
other theropods
If body size increase is accompanied by enhanced adaptations for hypercarnivory, then:
a) population density will decline, and
b) species will become more vulnerable to extinction.
-evolution of size leads to decrease in ability to adapt
evolution doesn’t care about extinction-just cares about fitness of individual-if bigger, easier to survive-evolution leads to improvement on individual level but extinction on species level
How fast could theropods run?
-Estimates done with modeling:
– Allosaurus & Tyrannosaurus 4-11m/s (9-25mph)
– (Much) faster speeds for smaller taxa
-look at modern animalis, mass to speed ratios-then try to do same thing for dinos, use other models to help
-t rex was probably not a fast runner-9-25 mph-so fast, but not cheetah fast-fast enough to run down a human at the higher end
-smaller dinos probably moved a lot faster
Was T. rex a predator or scavenger? Evidence for scavenger:
- Relatively small eyes
- Enhanced smell(smell rotting animals, draws them in)
- Relatively slow speed
- Tiny forelimbs
- Piercing teeth-for taking off big parts of flesh and crushing bones like modern hyenas
Was T. rex a predator or scavenger? Counterevidence to the scavenger evidence:
- Large absolute size of eyes even if relatively small for their head
- Smell can be used to find living as well as dead
- Prey were slow too-so didn’t matter than t rex was slow
- Some modern predators don’t have useful arms either – wolves, secretary birds, etc.
- Teeth similar to crocodiles
- Obligate scavengers (if only eat already dead pray-there’s an energetic cost-have to move around quickly, get to it before competitors, takes a lot of energy-so) need to be soaring vertebrates (i.e., vultures) due to energetic costs
- found an animal that was attacked by a T Rex and healed and survived-evidence that T Rex went after living animals
Was T. rex a predator or scavenger? answer:
-probably somewhere in the middle-T Rex was the biggest thing around-it’ll eat whatever it wants-probably wasn’t an obligate scavenger but an occassional scavenger
Tyrannosaur Growth
- Behavior probably changed during growth
- Younger individuals were smaller and faster
- Older individuals were slower and probably ate bigger prey
- High mortality among neonates-probably had a lot of offspring, prococious, went out to get prey, but these smaller young were probably prey themselves-so a lot died, but those who survived went to top of the food chain
Tyrannosaur Diversification
- May have tracked changes in sea level
- Changes in sea level may have led to isolation and migrations-led to speciation
- this is what gets done with modern animals esp birds-looking at why so many species, relate to environmental things
A holistic approach to theropods
-model skulls to look at biting, teeth to look at diet-lots of things going into this, holistic thing-looking at all diff aspects of Tyrannasaurus biology to figure out characteristics
Dinosaur Decomposition
- oviraptor nest with decayed skeletons found
- found evidence on bones of animal of flesh-eating beetles-same ones we see today
- use now to ready skeletons to get put in museum collections-get rid of all flesh
- used for forensic work too-can tell how long it’s been out based on how many life cycles of these beetles have happened
Major Plant Groups in the Mesozoic
- important cuz drove evolution of sauropods
- Pteridophytes
- Gymnosperms
- Angiosperms
Major Plant Groups in the Mesozoic: Pteridophytes
- vascular tissue & spores
- Horsetails
- Ferns
Major Plant Groups in the Mesozoic: Gymnosperms
- naked seed plants (have seeds, but not encased in fruit)
- Cycads
- Ginkgos
- Conifers
Major Plant Groups in the Mesozoic: Angiosperms
- have seeds, but encased in fruit-flowers turn into fruit
- flowering plants
Horsetails (Sphenophytes)
- Develop ‘fruiting body’ that releases spores
- Need water to germinate because they have spores
- Modern taxa (“Equisetum”) are small
- Mesozoic taxa reached 30P (10m) tall
- adults don’t really have leaves-young only have thin ones
- long, thin, flexible plants
- much more diverse group in the pst-much bigger part of ecosystem
Ferns
-Two stage life-cycle
– Sporophyte – gives off spores
– Gametophyte – a developing spore
-so basically like if egg and sperm left our bodies then lived on own for a while before coming together
-Need water to germinate
-Tree ferns grew to immense sizes (although not as large today)
Cycads
-Aka “sego palms”
-Dioecious -male and female plants are separate
– Male plants give off pollen
– Female plants have seeds
-Thick leaves to resist predawn
-Much more diverse in Mesozoic
Ginkgo
- One living species -“Ginkgo biloba”
- Dioecious-usually just see the males though?
- First ‘woody’ plants
- Stinky seeds that “reptiles” like
Conifers
-Modern cedars, cypresses, firs, junipers, pines, redwoods
-Mesozoic podocarps and “monkey puzzle trees”
– “Lollipop” morphology
– Restricted to southern continents today
-some are monoecious (having male and female reproductive structures), some dioecious
-now restricted to southern continents, but much more widely spread throughout mesozoic
Angiosperms
- Flowering plants
- First ones in the early Cretaceous-start to take over by end-but early on, limited -take over because they can grow very quickly-almost like weeds-come in and take over area that’s been recently cleared-so dominant group when you think of plants
- Often with male and female reproductive parts in the same flower
- Seeds covered by a fruit
- Many are faster growing than gymnosperms
- rise of Angiosperms coincides with rise in insect pollinators and herbivores
plant diversity over time (increased or decreased?) ____
increased for angiosperms-the rest stay about the same-except early vascular plants die out
Reconstructing a paleo-forest
- Permian (300Ma) forest from China with exquisite preservation
- Dominated by tree ferns with taller conifers and sphenophytes
- forests looked a lot diff than today
Climatic Variation across the face of the Earth Today-Location of the World’s Major Deserts:
all around these latitude lines (30 degrees north and south)-has to do with air circulation patterns-find diff plant communities today using this same reasoning
Climatic variation across the face of the Earth in the Jurassic
- Most of the plant (and dinosaur) diversity is in the midlatitudes (much like today. Equatorial regions more desert-like: hotter and dryer
- Due to hothouse conditions and continental position
- so we know kinda what the environment looked like back then, how it affected the plants and animals as climate changed
- by studying what happened in the past, may be able to get some knowledge of what happens in the future
Sauropods
-The largest vertebrates to walk the Earth!
-Originate in South America in the Triassic
-First radiation of dinosaurian herbivores
– Adapted to eat the tough plants of the midMesozoic (e.g., cycads & conifers)
-First extinction of a major dinosaur lineage – the prosauropods
-many early forms were still theropod-like
-400kg heart!! (about 900 pounds)
Titanosaurs were ____
the biggest animals that ever lived on land-but they weren’t born big
Triassic diversity
- a lot of diversity
- many early forms (of sauropods) were still theropod-like
sauropod head size
don’t need big heads cuz don’t do much chewing or processing in mouth-just using mouths to rip off plant material, swallow whole-then stomach does all the processing-fermentation, gastroliths
Sauropod Skull Modifications
-Large nares (nostrils)
– Move further posteriorly during their evolution
-Teeth built for scraping plants (not chewing)
-Two types of teeth
– Pencil (diplodocids)
– Thick leaf-like (brachiosaurs)
– Both probably for puncturing, not grinding
-Plant digestion by fermentation and gastroliths
Snorkeling Sauropods?
-An adaptation for living in the water?
– Probably not – too much pressure on the lungs
-maybe they had a trunk?
-many taxa that were found had nostrils pushed back, trunk-like structure-so maybe sauropods did have a trunk-not positive
-but the problem with this idea is that sauropods wouldn’t have sunk
Sauropod necks
-Elongated necks
-From both elongation of cervical vertebrae and increase in number
-Also elongate tails
-Thermoregulatory?
-Herbivory adaptation? so could get at higher trees
Neck Posture:
-straight up or held parallel to ground?
-probably not so upright-side to side, swing head, eat everything in a certain radius-so could get a lot of food
-some groups could lift head high
-Blood pressure estimates
-Computer modeling of neck motions
-Probably more side-to-side than up-down in most taxa
Apatosaurus
- genus of sauropod dinosaur that lived in North America during the Late Jurassic period
- range in age from about 154 to 150 million years ago
- cervical vertebrae were less elongated and more heavily constructed than those of Diplodocus and the bones of the leg were much stockier despite being longer, implying that Apatosaurus was a more robust animal
- The tail was held above the ground during normal locomotion
- Like all sauropods, Apatosaurus had only one claw on the forelimbs and three on its hindlimbs.
- skull similar to Diplodocus skull
- long/big
Diplodocus
- genus of diplodocid sauropod dinosaur
- double-beamed chevron bones located in the underside of the tail
- lived in what is now western North America at the end of the Jurassic Period
- classic dinosaur shape, long neck and tail, and four sturdy legs.
- For many years, it was the longest dinosaur known. Its great size may have been a deterrent to the predators Allosaurus and Ceratosaurus
Sauropod Neck Adaptations
-Pneumatized vertebrae-lots of air, open space
– Lighten neck (and support?)
– Air Sacs?
-Neck (nuchal) Ligaments-area for spine to attach?
sauropod vertebrae
- different vertebral joints allow for differing range of motion
- can compare these dino spines and necks to other animals-to understand how worked
- like suspension bridge? long tendon down neck and back that helped keep head up
- hydraulic necks-head heads up with air sacs-filled up air spaces with air, like balloon, helped keep head up
- but not all had long necks-brachytrachelopan didn’t
Sauropods-Adaptations for Quadrapedality
-Short hind limbs – Longer forelimbs in some taxa -Shorter distal elements – Humerus > radius/ulna – Femur > tibia/fibula -Graviportal posture
Sauropod feet
- Graviportal Digitigrade feet
- Still on toes, with a foot pad posteriorly
- similar to modern elephant feet
- Clawed Feet
- Enlarged digit 1 on forelimb with claw
- Claws on digits 1-3 in hindlimb (in later forms)
- forelimb more digitigrade, hindlimb more plantigrade, in both diplodocus and apatosaurus
were Sauropods tripedal?
- use tail as another leg?
- probably did not do this-or if did, not often-probably only for sexy time to help keep balance, use claw to hold onto females
Trackways reveal ____
- sociality and stance
- upright posture as you’d expect from dinos
- travelled in groups or herds-shows some sociality
Sauropodomorphs
- Worldwide distribution
- 2 major groups: Prosauropods and Sauropods
Sauropodomorphs: Prosauropods
- Late Triassic – Early Jurassic
- First extinction of a major dinosaur lineage
- Long, narrow skulls
- Serrated, leaf-like teeth
- Facultative bipeds – Front limbs shorter than hindlimbs -can walk on 1 or 4 legs
- 10 cervical vertebrae
- Not as large as later sauropods (2-10m)
- necks not very long
Plateosaurus
- one of the best known dinos-many skeletons found, many complete
- a genus of plateosaurid dinosaur that lived during the Late Triassic period, around 214 to 204 million years ago
- prosauropod
- As of 2011, two species are recognized: the type species P. engelhardti, and the slightly earlier P. gracilis
- a bipedal herbivore with a small skull on a long, mobile neck, sharp but plump plant-crushing teeth, powerful hind limbs, short but muscular arms and grasping hands with large claws on three fingers, possibly used for defence and feeding
- large variation in size
- usually lived 12-20 years
- mass death site suggests sociality
Sauropodomorph: Sauropods
-Mainly Jurassic – except Titanosaurs that last through Cretaceous, mostly in Gondwana -Enlarged coracoid (on pectoral girdle) -Claws on hind digits 1-3 ->12 cervical vertebrae (necks bigger) -Further elongate tails -More elaborate vertebrae -two major lineages
diplodocids(diplodocus) vs macronarians (camarasaurs, brachiosaurs, titanosaurs)-diplodocids:
- single nostril opening-nares posterior and between orbits
- procumbent, slender peg-like teeth at anterior margin of mouth
diplodocids(diplodocus) vs macronarians (camarasaurs, brachiosaurs, titanosaurs)-macronarians:
- single nostril opening-nares posterior and between orbits
- procumbent, slender peg-like teeth at anterior margin of mouth
Barosaurus
- a giant, long-tailed, long-necked, plant-eating dinosaur closely related to the more familiar Diplodocus.
- Upper Jurassic period
“Brontosaurus”
- Apatosaurus ajax was named first (by Marsh)
- Brontosaurus excelsus was named later (also by Marsh)
- Were found to be part of the same genus, and Apatosaurus has priority
- when you discover 2 species are actually the same thing, go with older name, forget the newer one
camarasaurids, brachiosaurids, titanosaurids
can lift heads higher, cuz have forelimbs on ground, not bipedal
some titanosaurids develop ____
- dermal armor
- why? species recognition thing? don’t really know-interesting
Dinosaur National Monument
-NE Utah
-Jurassic
-Specimens of:
– Apatosaurus
– Barosaurus
– Camarasaurus
– Diplodocus
Sauropod Diets
-Probably ate lower quality plant material – tough parts of conifers and cycads
-Large size may have helped with digesting poor quality plant material
-May have prevented overgrazing
-Plants adapted to sauropods
– Another Red Queen race that drove them to bigger sizes-led to gigantism in sauropods
marked ____ in the number of herbivores and angiosperms in the late Crestaceous
increase
what dominated the Late Jurassic
huge herbivores and conifers dominated the forests. Herbivores created open spaces that favor weedy opportunists (angiosperms)
what dominated the early cretaceous:
low browsing herbivores and first angiosperms
what dominated the late cretaceous:
diverse low browsing herbivores and diverse angiosperms
Ornithischia Novelties
- ‘Bird’ hips (reverse pubis) – possibly to make room for big stomachs
- Leaf-shaped teeth
- Lower jaw with predentary bone
- Network of bony ligaments (called ossified tendons in lab)
– stiffen backbone
Ornithischians made up of:
ornithopods, marginocephalians, thyreophorans
Horns and Spikes-which dinos have them?
Thyreophorans & Marginocephalians
Thyreophorans
“Armored Dinosaurs”
- Characterized by osteoderms – “skin bones” or scutes
- Probably another “Arms Race” with theropods -like when species increase in size-this is another solution, to develop armor
- Herbivorous – with some specific adaptations for eating plants (only theropods can be carnivorous-but not all theropods are carnivorous)
- Also characterized by post-orbital processes
Osteoderms
-Form in the connective tissue layers of the skin
-Multiple purposes in thyreoporans
– Defense, display (sexual selection or species recognition), thermoregulation (may have helped them regulate body temp)
-Also found on titanosaurs (sauropods), other diapsids, and edentate mammals
Thyreoporan herbivory adaptations
- Small, leaf-like teeth, inset from the edge of the jaw (probably for cheeks)
- but probably didn’t chew a whole lot with this tiny little teeth-mostly just tore stuff up and swallowed
- Beaks (rhamphotheca) for nipping plants
- Possibly long tongues that could extend to pull of plant material – we think they had this because they had well developed hyoids -bone between voice box and tongue-usually mean attachment for some sort of muscular tongue
- Wide thoracic regions-kind of barrel shaped – fermentation vats (for fermentation of plant material)
Thyreoporan bipedality? or quadrupedality?
-most of these guys were quadrupedal (walked on 4 legs)
-Large forelimb to hindlimb ratio (1:2)-hindlimbs relatively tall compared to forelimbs
– Thickened limbs
-Wide stance and slow gait
– Possibly semi-sprawling forelimbs
-Low browsers-probably kept heads relatively low-couldn’t lift highs very high
-but hold tail up a bit, head not completely down
solitary or social
- Mostly Solitary
- No ‘mass graves’
- Pinacosaurus burial site in Mongolia is the only site with multiple individuals, including juveniles
- so they probably weren’t very common or very social
early forms of Thyreoporans
- Early Jurassic of Laurasia
- Possibly bipedal (facultative-could choose to walk on 4 legs or 2 legs?- or obligate)
- but eventually this group of dinos had to become quadrupedal so later forms quadrupedal
- scutellosaurus (SW USA), scelidosaurus (england)
scutellosaurus
- an extinct genus of thyreophoran ornithischian dinosaur that lived approximately 196 million years ago during the early part of the Jurassic Period
- is classified in Thyreophora, the armoured dinosaurs
- bipedal
- one of the earliest representatives of the armored dinosaurs and the basalmost form discovered to date
- a small, lighly-built, ground-dwelling, herbivore, that could grow up to an estimated 1.175 m (3.9 ft) long
scelidosaurus
-a genus of herbivorous armoured ornithischian dinosaur from the early Jurassic
-known for their excellent preservation. Scelidosaurus has been called the earliest complete dinosaur
-Only one species, Scelidosaurus harrisonii, is considered valid today
0about 4 metres (13 ft) long
-largely quadrupedal animal, feeding on low scrubby plants, the parts of which were bitten off by the small, elongated, head to be processed in the large gut.
-Scelidosaurus was lightly armoured, protected by long horizontal rows of keeled oval scutes, that stretched along the neck, back and tail.
-a basal member of the Thyreophora
-One of the oldest known and most “primitive” of the thyreophorans
Ankylosaurs
-mid Jurassic – end Cretaceous
-5-9m long
-Laurasia and Australia
– Maybe S. America & Antarctica
– Polar specimens known
-Conservative body plan– only change in size
-Two groups
– Ankylosaurids and Nodosaurids
– Differ in skull shape and placement of osteodern-but still basically have same body plan
Ankylosaur Skulls
- Broad skulls with armor covering sutures and the supratemporal fenestrae
- like had bones in scalp that eventually fused with skull-covered temporal fenestra, diff holes-all these little bones osteoderms fused to the skull
Ankylosaur brains
small
Ankylosaur teeth
-Teeth have cingula – ridges around the base
ankylosaurs nostrils-what do they indicate?
- tooting ankylosaurs?
- large blood vessels
- vocalization? - communication
- physiology? temperature regulation
- sensory? smelling
- weird complicated nostrils-maybe for some sort of mating call?-looks like trumpet where can make noise, modify noises
- some people think it was for temperature regulation-work like turbinates in nasal passages
- or maybe it was a sensory thing-neuron receptors in there for smelling things
- most like vocalization
Ankylosaur Pelves
- Modified Pelves
- For bearing weight of armor
- Synsacrum (fused vertebrae and pelvis) with horizontal ilium
- Closed acetabula (lost hole there that all dinos have) and reduced pubis-so big steel girder pelvic bones fused with vertebrae
Ankylosaur tails
- Tail Spikes and Clubs
- Made of enlarged osteoderms
- Linked tail vertebrae
- could swing around
- Possibly for display (sexual selection)
- Similar to glyptodonts
- maybe used for defense-or used for male on male aggression to fight for females
could ankylosaur swing their tail clubs?
probably, at least the smaller ones could
Stegosaurs
- Laurasia (mainly China), Africa, Australia
- mid Jurassic to mid Cretaceous
- 3-9m long
- Parasagidal (near the midline) plate-like osteoderms (raised from the skin some)– Also small neck osteoderms
- Tiny skulls – EQs similar to sauropods (small area for brains-most of skull not brains but nasal passage and stuff)
- Horizontal tail spikes (smaller)
Stegosaurus plates
- Alternating arrangement
- Possibly thermoregulatory and/or for display-could’ve flushed them with blood (blood vessels there) and changed color-to attract females or warn males
- or maybe both (thermal and display)
did humans and dinos exist at the same time?
No!!!
Miragaia longicollum
- late Jurassic of Portugal
- sauropod-mimic stegosaur?
stegosaurs and ankylosaurs
- these 2 groups kind of replace each other
- more stegosaurs in the late jurassic
- more ankylosaurs in the late Crestaceous
- so looks like there was an armored dino niche-only 1 group could really fill it at a time-so don’t have a lot of stegosaurs and ankylosaurs existed at the same time
Marginocephalia
“Margin Heads”
- Relatively numerous in fossil record (at least ceratopsians)
- Very endemic – restricted to Laurasian Cretaceous
- Taxonomically complex
- Taxa are probably “over-split”
- they were finding individuals of the same species and naming them diff things-only later this got fixed-but some evidence there were multiple taxa in some cases
- still arguments going on about how diverse Marginocephalia was
- debate partly cuz no modern analogs of these species today-so difficult
Triceratops taxonomy problems
- fossils show problems of oversplitting, and complications of ontogeny
- misidentified-turns out triceratops was just older individual of torosaurus
- but new research says they may have been diff species
Ceratopsians head size
Huge Heads!
- Ceratopsians have largest head/body ratio of any terrestrial animal
- heads 1/3 of their body size (in adults)
- big cuz of the frills that cover neck region and back of head
- Formed by parietal & squamosal bones
Ceratopsians Herbivorous adaptations
dental batteries, gastroliths
Pachycephalosaurs Herbivorous adaptations
heterodont dentition
Pachycephalosaurs locomotion
bipedal
Ceratopsians locomotion
facultative bipeds (early) & quadrupedal (late) – Sprawling (on side) or upright (below them) forelimbs? important when thinking about speed -trackways and comparison to modern taxa say upright stance -so could probably run relatively quickly for short bursts
Sexual Selection
-Increases fitness by increasing the number of mates (and therefore offspring and genes in the next generation)
Sexual Selection classi modern example
Artiodactyls (horned hoofed mammals)
sexual selection traits-Horns
Bony core with keratin sheath-Permanent (cows, sheep, goats, African antelope)
sexual selection traits-antlers
Bony core with velvet sheath-Shed yearly (deer, elk, moose)
sexual selection traits-horns AND antlers
-Used by males for display and in intraspecific fights (over females)
Pachycephalosaurs
-North America and China, Cretaceous
-1-3m long, one 8m species
-what’s unique about these guys are their thickened skulls – fused frontals and parietals -huge domes on their heads
9up to 20cm thick!
-thickened dome of cranium
2 types of pachycephalosaur
-flat-headed (ex: homocephaloids) and dome-headed (ex: pachycephalosaurs)
Evidence for head butting
- Thickened skulls
- Scars on skulls -skulls cracked when head butting
- Strong neck & vertebral articulations
- Biomechanical analysis
- Possible sexual dimorphism-females have lower domes, males have bigger domes-speaks to males fighting over females
- compared scars in these dino skulls to scars in skulls of modern head-butting animals-the sorts of scars matched
but what about the flat headed ones? did they head butt?
- may have been more of head pushers
- a couple of lizards do this
- lock heads and push back and forth in some sort of display
- hit heads, move back and forth-flank butting
- *none of these are mutually exclusive-maybe did a few of these things**
Ceratopsians
-Late Jurassic (one taxon) to Late Cretaceous of N. America and China
– Probably migration from Asia to N. America
-5-9m long
-Herbivory adaptations:
– Rostral bone
– Dental batteries– Powerful jaws – Expanded cheek bones -for muscle attachment-so may have had powerful muscles to bite off plant material
did ceratopsians duel?
- horns and frills for sexual selection and species recognition, not so much defense
- one guy looked at where you see injuries on skulls-exactly where would expect if locking horns-not so many scars on nostrils and other areas-mostly on horns
Protoceratops
-slightly later form than in last slide
-Primitive
– facultative biped?
– Frill with no horns -frills came before the horn
-2.5m
-Nest site with juveniles-so social
-Sexual dimorphic-starting to see 2 diff forms-1 male, 1 female
-Multiple mass burial sites known in Mongolia
Centrosaurines
- large nose horn
- small eye horns
- larger nares & frills
- e.g. Centrosaurus
Chasmosaurines
- Small nose horn
- Large eye horns
- Smaller nares & frills
- E.g., Triceratops
did all centrosaurines have horns?
-No-some centrosaurines had thickened keratin (nail-like) pads instead of central horns
Ceratopsian diversity
- very very diverse
- why do they have this huge diversity?
- maybe a bunch were just dff ages of same species-but this doesn’t explain all of it-a lot of real diversity, more than would expect
- one explanation is the “species pump”
The “species pump”
- big shallow sea that divides west from east
- these guys probably lived in the lowlands between the seaway and the mountains
- the sea changed sea level-sea level went up and down over cretaceous-cyclical-happened multiple times over Cretaceous
- Repeated rise and fall of interior seaway, could have fragmented populations, leading to speciation-the rise and fall of seaway probably isolated species-separating members of same species-evolve separately-once come back together again later, too diff, no longer same species, can’t mate-this happened again and again, leading to lots of speciation and variation
- This has been shown for modern animals and glacial advances
“species pump” example
warbler birds-during ice ages glaciers advanced down north america then retreated-fragmented these populations of birds, some retreat down to Mexico, or Florida, or the Caribbean-may have been this species pump that generated all this diversity in warblers-and this has been shown as happening for other birds and other mammals too-so the advance of glaciers works in the same way as the advance of seaways did in the past
Ceratopsians-social or not
- social beasts
- maybe flooding event, all got buried at once
- very social
- lived like modern social animals
what was found on some ceratopsian fossils?
- T rex bite marks
- seratopsian pelvis with t rex teeth embedded in it-unclear if t rex attacked and killed it or scavenged it-cuz unhealed, so animal was killed or already dead, cuz didn’t heal after
- evidence of predation
Ornithopods!!
“Bird Feet”
-The herding herbivores of the Late Mesozoic
– Similar to modern bovids, zebras, etc.
– Best record of social structure in dinosaurs
-Efficient plant processing
– Possibly most efficient chewing system in vertebrates
-Bipeds or facultative quadrapeds
– Hoofed fingers on forelimbs in some forms
– Ossified tail tendons
-1-12m long
-herbivores
-flocks and herds
Ornithopod adaptations to herbivorivity
-Efficient Herbivores
-Jaw joint below the tooth row
-Dental batteries
-Cranial kinesis
-“Duck-Bill”
– In later forms
-Diversification may have been caused by adaptations to new ecosystems
-tooth wear is similar to modern ungulates
continental breakup creates ____
new ecosystems and population fragmentation
why do ornithopods exist in flocks and herds?
-Safety in numbers
Heterodontosaurids
-Early Jurassic of Africa
-Heterodont dentition – ‘canines’ similar to mouse deer-didn’t have dental batteries like later forms
-Bipedal
– Long tails -probably used for balance
– Fused distal elements -means they’re running animals
-Possibly diggers -robust forearms, may have used front arms for digging
-May not be ornithopods, but primitive ornithischians
Fruitadens
-Smallest known ornithischian
– 65-75cm
“Hypsilophodontids”
- Mid Jurassic to Late Cretaceous
- Paraphyletic grouping of relatively primitive ornithopods
- First to show some of the adaptations for efficient herbivory.
- Still relatively small (<2m)
- Once thought to be arboreal
Iguanodontids
-Late Jurassic to end Cretaceous
-Contains the majority of the ornithopod taxa
– Iguanodon
– Hadrosaurs
– Lambeosaurs
-Some forms had elongate neural spines, similar to spinosaurs-display?-thermoregulation?
-Many were probably facultative quadrupeds
– Dagger thumb on forelimb-unclear what for
– Opposable pinky
-some had hooves
Hadrosaurs
- “Duck-bills”
- Most developed dental batteries
- Unguals (hooves) on hind limb
- Long forelimbs
- rise after the decline of sauropods
Lambeosaurs
- “Hollow-crested”
- Large head ornaments
- rise after the decline of sauropods
Steps of Dinosaur Reproduction
- Attracting a mate
- Sexual Selection
- Mating
- Building Nests & Laying Eggs
- Parental Care (if present)
- Growth
We have evidence for every step in dinosaurs, many of it from ornithopods!
Secondary Sexual Characters
-Often maladaptive structures-makes it harder to fly or run maybe-but trait still exists because for display or something, helps in sexual selection-ex: cresrs
-to say something is a secondary sexual characters, have to eliminate other possible uses:
-Defense/offense?-that’s a possible use, but not true for all seratopsians-crests hollow
-Thermoregulation?-not these guys
– Sexual selection(males attracting females)/species recognition? (recognizing another member of your species that you can mate with)-What should we look for to prove this?
If traits are for sexual selection, ….
- they shouldn’t develop until animals are adults (adult features)
- there should be sexual dimorphism
sexual selection: Adult features (lambeosaurs)
traits shouldn’t develop until animals are adults (i.e., when they’re ready to mate)
-lambeosaur growth series show that their cranial crests don’t develop until adults?-so for sexual selection?
sexual selection: sexual dimorphism (lambeosaurs, theropods)
- There should be different forms in the same population
- lambeosaur sexual dimorphism
- theropod dimorphism: females bigger than males, as w many dinos
But why is there Sexual Selection
-Usually involves male/male competition or female choice
-Why are males usually the ones fighting each other, or for the attention of females?
– Unequal investment in resources
– Eggs are much more costly than sperm
– Also, females usually care for the young, so also have to invest resources in that process
Runaway Sexual Selection
-Often sexual selection can push things too far and they can become maladaptive
Runaway Sexual Selection in Dinosaurs
- ridiculously giant spikes and things-probably sexual selection
- may have been the case in some dinos with headgear
- crooning headgear
- dewlap and head sacs-had head sacs that blew up/inflated to attract mates-colorful sometimes
- some of these didn’t fossilize well
- also see in mammal groups-elephants to make disturbing calls, fight each other, bite noses
parasaurolophid headgear
headgear for making mating calls-did study, used CT scans, saw the inflating sacs
dinosaur sex/mating in dinos
- made difficult by the back spikes and giant size
- closest modern example are elephants, but still not a good comparison
- cloaca kiss-small penis or none-shoot sperm into female’s cloaca
Mating in Most Non-amniotes
-Cloaca (“Sewer”): posterior opening that serves as the only opening for the intestinal, reproductive, and urinary tracts of certain animal species– one hole for everything
-Female lays eggs in water , maybe some sort of nest
-Male comes and fertilizes them
-Sometimes this is done simultaneously-like frogs
-Rarely is fertilization internal-male sperms inserted into female
– E.g. sharks
Mating in Amniotes
-Fertilization must occur internally
– Sperm stored in female after mating-sometimes she can choose sperm wants to use, cuz often fertilized by multiple males
– Eggs grow inside female in oviducts
-Still have cloaca
-Some taxa appose cloaca
-Some males have protuberances to facilitate transfer of sperm
-Mammals start to divide up the cloaca
Evidence of cloacal protuberances in theropods
-have evidence of male and female t rex-look similar but male has a few extra bones-people think these extra bones for muscles-to help them evert their penis-other species do this (he mentioned which one but I missed it)
Laying Eggs-number of eggs (r vs k selection)
– r selection – lots of offspring, little parental investment
– K selection – few offspring and lots of parental investment
laying eggs/number of eggs affects factors like:
– Clutch size-how many eggs you have at any one time
– Parental care-have little parental care, k has a lot
– Growth rates -animals w/o a lot of parental care grow relatively quickly, while w k, grow slowly
Dinosaur Egg Laying
-Dinosaur clutches have 2-30 eggs– Similar to birds-birds are more k selective than r selective
– Modern large reptiles lay >100 eggs
-Eggs produced in two oviducts
sexual dimorphism due to ___ ____
- egg laying
- female birds have more spongy bone, and this is seen in dinosaurs-why? using the minerals they’d use to make bone, to make eggs instead
- see this in dinos too
Discovery of hadrosaur nests in upland areas.
- Laid eggs in shallow depressions and covered them with vegetation-similar to some modern reptiles like crocs
- There is evidence they used the same sites from year to year. see this in modern birds
- Embryos indicate the young were able to walk when born-even though small-a little diff from birds
- Also known for sauropods and other taxa
- when you look at the spacing of the nests-distance between them one hadrosaur away-one adult size apart-space themselves out on landscapes-like modern birds
dinosaurs building nests
- sweep out sand/dirt to build nest
- sauropods had hind limbs with claws on them-like turtles-use to dig
- brooding in theropod dinos-dinos did brood
Modern analogs
to dino egg laying
- crocodilians burt their eggs partially and cover them with vegetation
- the warmth of the decomposing vegetation speeds embryo development-so didn’t need to sit on the nest (brood)-but they did guard the nest
- Female crocodilians guard their nests, often lying on or near them.
- rookeries and site fidelity in modern birds-Anacapa island-go to same spot every year to lay eggs
- all of this pointing to dinos being similar to birds and modern reptiles-but more towards birds
- nest collectivity
why was there nest collectivity
- protection
- adults protect the infants from predators
Dinosaur Embryos and Neonates
- Many dinosaur embryos and newborns are known
- Herbivores tend to be altricial, Carnivores tend to be precocial
- Both are born small and show quick growth rates and allometric changes -changed shape as they grew
- dinos grow vastly bigger than size born at-as grow bigger, habitat and where hunt changes-young don’t hunt in same niches as adults
- newborns have little extra bump on nose-used to break out of shell when hatching-lost pretty quickly after birth-some dino embryons that show the bump/egg tooth
Dinosaur Embryos and Neonates -herbivores
- Herbivores tend to be altricial (helpless-can’t do much on own)
- Carni
Dinosaur Embryos and Neonates -carnivores
-Carnivores tend to be precocial (hunt on own soon after birth-not hunting same things as adult, but can kind of take care of themselves)
Dinosaur parental care
-Some nest sites have evidence that young stayed in nests after being born
– (fossils of) Larger-sized individuals found in the nests
– Broken egg shells
-Level of care probably different in different taxa
Dinosaur lactation?
yes, but not breast feeding-adult goes out, catches food, partially digests, bring back up into mouth, feed to young–that happens with birds, may be the case with dinos
nest predation
-nice evidence of nest predation-nest found with eggs and snake in it-snake died in the nest, buried by some event
Dinosaur Growth Rates
- Dinos had a 3 part growth curve, especially the biggest ones
- Maybe there was parental care in the first part of the curve
Mesozoic communities-Dinosaurs in their ecosystems
-Animals don’t live in a biological vacuum
-Not all interactions are predator/prey
-Dinosaurs are the “charismatic megafauna” of the Mesozoic-They’re popular and consequently get all the attention-dinos get all attention but were small part of ecosystem-many other species, organisms, just not as exciting so get no attention
– Similar to large mammals of today and the Pleistocene
Ecosystems are embedded in ____
climates
What is weather?
– Short-term changes in wind, pressure, temperature, cloud cover, precipitation, etc.
What is climate?
-the long-term average of weather
– More stable - deserts are always deserts, with a relatively low rainfall, but at specific times they can get a lot of rain.
How do we find out climates in the past?
- Historical records only go back about 400yrs (longer in some areas)
- so use proxy data
proxy data
Inference from indirect means
Examples of proxy data
– Glacial deposits-glaciers scrape along the ground as move, drop sediment
– Leaf shape-leaves in tropical areas diff shapes than in temperate areas-in tropical environment, heart shaped-in temperate, serrated edges
– Tree Rings-give us some evidence of how long the growing season was
– Oxygen Isotopes-oxygen comes in 2 diff types, one heavier than other, look at balance of those 2 things to look at climates of the past
– Others…
Colorado Plateau
-Centered on Four Corners
-Geologically stable since the Mesozoic
– Upraised in the Cenozoic
-Dramatic Geology
– Drained by the Colorado River
– Arid climate
-Site of many of the best North American dinosaur sites
– Incl. Dinosaur NM & Cleveland-Lloyd Dino Quarry
why is the Colorado Plateau so important when it comes to dinos?
-since the mesozoic this area has been relatively stable-not a lot of faulting and burial that may have ruined things-really good place to find dino fossils-also whole rock was pushed up in the cenozoic, so relatively high, not a lot of precipitation, sediment, stays, easier to find dinos
Climatic variation across the face of the Earth in the Triassic
- Equatorial deserts
- Large fluctuations in weather due to large continents
- Temperatures 7-10 degrees C (13-18 degrees F) hotter than today
Triassic Colorado Plateau
-Highlands to the west and east
– Due to subduction off the west coast
-Wet areas in between, with lakes and rivers draining to the northwest
-Deposition of the Chinle Formation
Petrified Forest National Park
-East-central Arizona
-Late Triassic – 225Ma
-Chinle Forma-on exposed as badlands
-Contains numerous fossil trees, as well as other plant and animal fossils
– Many tree fossils are of large conifers
Geologic Formations
-Fundamental units of stratigraphy – Defining cohesive units of sedimentary rocks – Laterally continuous – Subdivided into members – Grouped into groups
Inhabitants of Petrified Forest
- Metaposaurs
- Therapsids
- Sphenodontans
- Procolophonids
Therapsids
-Inhabitant of Petrified Forest
-Large (3.5m) herbivorous syanpsids-largest herbivore of the time
– Permian survivors
3 major insect groups first appear in the Triassic
- Diptera – flies and mosquitos
- Hymenoptera – hornets, bees, wasps, and ants
- Coleoptera - beetles
mesozoic fleas-what do they indicate?
- fleas don’t live on scales, but they do live on feathers…
- so dinos probably had feathers
Coelophysids
-Mainly small, predatory dinosaurs
-Coelophysis – most numerous dinosaur fossil
– Ghost Ranch Site, NM-mass death-already talked about this
-were they cannibals? probably not-already talked about this too-originally thought were, remains of same species in fossil’s stomach, but now think it’s a different species
Triassic Dinosaurs -big or small part of ecosystem
-Relatively small parts of ecosystems
Triassic Dinosaurs -Three waves of diversification
– Prosauropods– None in North America, but present on other continents
– Small theropods – Coelophysis and other small taxa
– Ornithischians – only in South America
Why did dinos diversify and dominate?
-Perhaps dinosaurs had a “key adaptation” that allowed them to diversify and dominate?
– Upright walking?
– Endothermy?
-2 models for dino takeover in triassic-competitive displacement vs. opportunistic-already talked about this-probably by luck mostly, happened to be good conditions for them
Jurassic Paleogeography
- first time dinos really dominating?
- Pangea is beginning to break up
- Subduction still occurring off the west coast of North America
Jurassic Colorado Plateau
- Deposition of the Morrison Formation
- Western US more arid, with rivers, and accompanying wetlands, draining to the forming inland sea to the northeast
- Extensive sand dunes in the Four Corners area
- Still “hot house”-hotter than it is today
Modern Serengeti
-Relatively arid grasslands
– In Jurassic “grasses” would have been ferns and horsetails -no real grasses, but things filling in the grass low niche
-Many riparian strips along waterways, stream beds, supporting thicker vegetation-similar in age to the Solnhofen limestone
Morrison Formation
- 146-156Ma
- Deposited in braided streams, flood plains, swamplands
- Similar in age to Solnhofen Limestone
- Found throughout the Colorado Plateau and northward into Canada
Dinosaur National Monument
-NE Utah Morrison Formation
-Jurassic
-Specimens of:
– Apatosaurus
– Barosaurus
– Camarasaurus
– Diplodocus
– Stegosaurus
– Dryosaurus
– Allosaurus
– Torvosaurus
– Ceratosaurus
(last 3 carnivores, the rest herbivores)
Cleveland-Lloyd Dinosaur Quarry
-Central UT
-Morrison Formation
-Species Counts:
– 44 Allosaurus
– 6 other theropods
– 9 sauropods
– 5 ornithopods
– 4 Stegosaurus
-Predator Trap!… or was it a drought assemblage?
Cleveland-Lloyd Dinosaur Quarry -predator trap or drought assemblage?
-Predator Trap! Locality was in sticky mud near a river bank
… or was it a drought assemblage
-The bones don’t seem to have been transported or scavenged
-Bones are crushed and
-Many sub-adult theropods (Allosaurus) represented
-May have been a catastrophic drought event at a watering hole
-could’ve been either-mix of both? but probably more latter
Non-Dinosaurs of the Jurassic World: Land
frogs, salamanders, turtles, lizards, snakes, small mammals
– Looking more like today at the small end of things
Non-Dinosaurs of the Jurassic World: Seas
coral reefs, ammonites, sharks, plesiosaurs, icthyosaurs
Non-Dinosaurs of the Jurassic World: Skies
first birds, both groups of pterosaurs
Jurassic Herbivores
- Food types can be inferred from tooth wear and energy content
- High browsers vs. Low browsers
Jurassic Herbivores-high browsers
- Camarasaurus, Brachiosaurus
- ate conifers and cycads
Jurassic Herbivores-low browsers
– Diplodocus, Apatosaurus, Stegosaurus, Gargoyleosaurus (ankylosaur) ornithopods (Dryosaurus & Camptosaurus)
– Probably also includes young high browsers
– Horsetails and low ferns (no grass!)
Jurassic Carnivores-small:
-10kg to 300kg – Koparion (Deinonychosaurid) – Tanycolagreus (Coelosaur) – Stokesosaurus (Coelosaur) – Marshosaurus (Tetanurid)
Jurassic Carnivores-large:
-1000kg to 2000kg
– Allosaurus (Allosaurid)-Most numerous taxon
– Ceratosaurus (Ceratosaur)
– Torvosaurus (Tetanurid)
***Largest taxa are still half the size of T. rex
Jurassic Ecosystem Energetics -large animal requirements (to get enough energy to sustain self)
-Large animals need more food & land, and tend to be at smaller population sizes & densities
– Safety mostly from size-so more about finding food than running away (more about getting away for smaller animals)
Large herbivore (sauropod) needs ____ per month to sustain itself
270 acres (300 football fields
Large carnivore needs ____ per day of meat
10kg
Carnivores probably ate….
smaller herbivores and juvenile sauropods
Sauropods may have changed the ____
- climate
- methane in atmosphere increased as sauropods thrived-contributed to global warming?
Mid-Cretaceous Paleogeography
• Western US as island ‘continent’
– interior seaway in North America due to high sea levels
• Less fluctuation in climate, and stable tropics/subtropics into high latitudes
Late Cretaceous Paleogeography
-Retreat of Interior Seaway connects east & west North America
Colorado Plateau Paleogeography
- Mainly tropical/subtropical
- Many transgressions/regressions of seaway
Grand Staircase-Escalante National Monument
-South-central Utah
-Deposits of:
– Chinle Formation
– Morrison Formation
– Kaiparowits Formation
74-76Ma
The Grand Staircase
- Record of near continuous deposition on the Colorado Plateau from Paleozoic through Mesozoic
- Extends from the Grand Canyon to southern Utah
Rise of Angiosperms
-During Cretaceous
-Occupy many habitats and grow relatively quickly
-Trees
– Beech, maple, oak, magnolia
-Still no grasses
– Herbaceous shrubs fill ground cover niche
-Hops, buttercups, nettles
Latitudinal Variation
-Comparison with more northern faunas reveal differences in faunas
– Dinosaur Provincial Park Alberta, Canada
Over 30 species of dinosaur – none the same as Kaiparowits
-Seems contra to large dinosaurs (and large herds of dinosaurs) needing lots of space.
How do we explain this Latitudinal Variation ?
- Some variation in plant communities north and south
- dinos as mesotherms
- probably needed less space than similar-sized endotherms/as modern herbivores, cuz not full endotherms or ectotherms-somewhere in between
- some migration into highlands allowed for some larger ranges
Chronological Variation
-Changeover in species through time in the Cretaceous
-Possibly due to “Species Pump”-like we discussed earlier
– Turnover pulses linked to environmental change
-Speciation is caused by:
– Isolation
– Subsequent evolution
Similarity in niches across time and space
- Although different taxa may be present at different times and places, they oren fill the same niches (jobs in the ecosystems)
- Example: compare the modern Serengeti and Yellowstone ecosystems
The rise of T. rex
-By the end of the Cretaceous it is the ONLY large predatory dinosaur
-Partly due to Evolutionary Ratchet
-Partly due to expansion of range
– Interior Seaway dries up
-Found in every habitat across the Late Cretaceous
-but dinosaurs weren’t the only predators-crocodilian-like feeding traces found on ornithischian dinos
Overview: Triassic
limited diversity of dinosaurs (mainly coelophysids and prosauropods) arer they replace non-dinosaur taxa
Overview: Jurassic
– Increasing diversity dominated by sauropods and mid-sized carnivores
– Small animals similar to today-small carnivores?
Overview: Cretaceous
- increase in diversity, especially in herbivores.
- Increase in size across taxa, except for many small theropods – Rise in angiosperms
dinos were at _____ before they went extinct
their most diverse
Cretaceous was a time of ___ seas
abundant, warm, shallow
what group returns to the sea in the mesozoic?
Reptiles
many reptile groups thought to have been sea-going because they….
- are found in marine sediments
- have many adaptations for aquatic life
Marine Reptile Characters
-Modified Skulls – Anapsids or Euryapsids -Large forms may have been endothermic homeotherms – Evidence from isotopes supports this – May have helped them rule the seas!
synapsid
1 hole behind eye
diapsid
2 holes behind eye
anapsid
no holes behind the eye-some spices derived from diapsids-lost holes?-some dinos have this
euryapsid
-1 hole behind the eye, but in diff place than synapsids-higher up, oval-these guys derived from diapsids probably-lost bottom hole behind eye-becomes little dent at bottom of skull-emargination-remnant of that hole
_____ and _____ may be modified diapsids
- Euryapsids and anapsids
- Carved out area formed perhaps by loss of bony bar beneath lower temporal fenestra
Mesozoic reptile invasions of sea
-Triassic:
- ichthyosaurs, placodonts, nothosaurs and plesiosaurs, pliosaurs (all “euryapsids”, the latter 3 were sauropterygians)
– May represent one or a few separate invasions of the ocean
– May or may not be closely related
– All died out by the end of the Mesozoic
-sea turtles (“anapsids”)
– Originated in Late Triassic, became common in Cretaceous
Mesozoic reptile invasions of sea-Jurassic:
-crocodiles (diapsids—archosaurs)
– Were mostly terrestrial during the Triassic, but many forms were completely marine by Jurassic
Mesozoic reptile invasions of sea-Cretaceous:
mosasaurs (diapsids—lizards) – Died out at the K/T extinction event
Nothosaurs
- possibly analogous to seals, sea lions, walruses
- hands/feet not very modified (webbed, not paddles), ilium not attached to backbone, large upper temporal fenestra; bone lost beneath lower one?, nostril moved back, up to 4m long, shoulder blades and hips beneath body, more robust arms than legs, piscivore dentition (so ate fish)
- nothosaurs probably a primitive group for the first venture into the water-there are a few groups that are derived from them
plesiosaurs
- Medium (2 m) to large (20 m) marine predators-very big
- Probably evolved from nothosaurs.
- there are transitional forms
- better suited to life in the water than nothosaurs.
- Could use paddles for forward propulsion and lift (like penguin)-wing like arms
- Significant side-to-side motion allowed in neck.
- more weight -helps keep them upright in water
- nostril, orbit, upper temporal fenestra-then embayment (remnant lower temporal fenestra?)
- hips and shoulders well below back
- enlarged gastralia (belly ribs)
- diving
plesiosaur paddles
- bones more uniform in hand/foot, plus extra phalanges for a larger, smaller paddle
- they’ve modified pretty much the whole limb-all flattened and shortened
plesiosaur skulls-and what they imply
plesiosaur skulls had a huge upper temporal fenestra and pronounced sagittal crest, implying ridiculously strong jaw snapping muscles
plesiosaur neck
- REALLY long neck-probably to help them catch fish
- neck was really mobile too (flexible)-don’t have the interlocking vertebrae, vertebrae more flexible, free to move neck more
- muscular
plesiosaur diet
tooth form, tooth marks, and gut contents show most plesiosaurs usually ate fish, but some larger species (with bigger heads) ate other marine reptiles
plesiosaurs adaptations for diving
- swallowed stones
- had thick gastralia, allowing them to dive down
- manatees had thickened ribs for similar reason
- probably also for balance, to keep them upright
plesiosaur egg-laying
- plesiosaurs were aquatic, but may have come to land to lay eggs
- some creatures in the water stopped laying eggs altogether, started giving birth to live young
Ichthyosaurs
the best-adapted reptile swimmers
General information:
-Up to 2-4 m long.
-Common for 155 million years of the Mesozoic.
-Had a worldwide distribution.
-Many may have been cephalopod prey specialists
-Largest forms may have been similar to modern orcas (killer whales) - macropredatory
-giant eyes to let as much light as possible when diving very deep-little bones around it to support this eye
-may have dove deep (>600 m)
-compact fins, thick body, ilium way below back, even head is streamlined, nostril moved back, sclerotic ring (bondy support for eye)
Ichthyosaurs-shape of fins known from…
- …..carbonaceous outline in well-preserved specimens
- can see outlines of flippers-can see they had a dorsal fin, like dolphins now-flute like tail, similar to sharks-swam similar to sharks-side by side-as opposed to whales that swim up and down-so these guys are more like fish-has to do with reptilian ancestry
Ichthyosaurs bend in tail
- seen in all well-preserved Jurassic-Cretaceous ichthyosaurs
- formed from wedge-shaped vertebrae in that part of tail-so it’s 1 side of tail/fin at the end
Ichthyosaurs birth
- gave birth to live young
- came out tail first, as in whales
- ichthyosaurs probably didn’t come to land at all
- fossils found with juvenile coming out of mother-died in the middle of childbirth, then fossilized like that? more likely that died, fell to bottom of ocean, bloated as decomposed-that bloating pushed the dead juvenile young out of birth canal
Ichthyosaur diving adaptations/evidence
- Ichthyosaurs may have dove deep (>600 m):
- had nostrils, needed to breathe oxygen-so needed to store oxygen like dolphins
- Large thick body, barrel shaped chest, provides stores of oxygen-also store oxygen in muscle tissue in abdomen
- Outermost layer of ichthyosaur bones spongy and lightweight, as in other divers.
- Some show decompression injuries
- need to come back up to air very slowly so don’t die from changing in nitrogen levels so quickly-some of these guys have these injuries from this, came up too fast
- Streamlined body (convergent with dolphins), allowing for faster descent/ascent and so deeper dives.
Evolution towards a better swimming ichthyosaur
- From lizard-like to dolphin-like.
- Vertebrae got taller, shorter, and more numerous, making a stiff, tuna-like body.
- Less wasted motion so animal is can swim further, and needs to come up for air less frequently
- triassic forms were more lizard like, okay swimmers, could only be in shallow water
- cretaceous forms more dolphin-like, can dive deep-evolving to fill new niches
- better swimmers-using just tail (like whales?) and can move a lot
Mosasaurs
- gigantic marine lizards of the Cretaceous
- Large (up to 12 m long) oceanic reptiles closely related to lizards (and possibly snakes).
- Are found in sediments worldwide.
- Were the dominant marine reptile in many oceans of the Cretaceous
- Some smaller forms may have been freshwater
- Note features indicating aquatic life (e.g., hip and shoulder girdle placement)
- fins less paddle like
- intramandibular joint-allowed them to have a stronger bite
Mosasaur diet
- probably eating some of the shell sephonites?? at the time-squid or octopus that live in a shell-actually have some proof of this-amniote found with mososaur tooth marks
- but big enough that they probably ate whatever they wanted:
- gut contents of mosasaurs include: large fish, sharks, other mosasaurs, molluscs, an ocean-diving bird, etc.
- evidence: healed wound marks on some of these that matched other individuals-indicate they occasionally fought each other
Mosasaur birth
Mosasaurs may have had live birth!
-Live birth evolves over 100 times in reptiles.-so not that strange, happens a lot
Turtles
- Turtles originate in Triassic, diversify in Cretaceous
- Largest turtle ever lived in Cretaceous seas
- related/similar to modern snapping turtles?
ocepechelon
- from morocco
- giant suction-feeding turtle from the Cretaceous
archelon ischyros
snapping giant
Origin of the turtle shell
- Involved broadening of the ribs and vertebrae
- Movement of scapula inside the rib cage
- shell of the turtle actually ribs, form the shell
- Evidence from paleontology, histology, and development-have really good evidence for how it happened now
some archosaurs…
took the the sea! like Deinosuchus
were there any aquatic dinosaurs?
-no dinos that were aquatic (except maybe Spinosaurus? which we talked about)-but some archosaurs moved to water-like crocodilians
what happened to archosaurs that moved into the water?
-once in water, fully marine, don’t need to support weight in more cuz in water-so get really big-this happened to crocs too
freshwater supercroc (sarcosuchus imperator)
- huge!
- had over 100 teeth, moveable bone at front of snout
- 13m long, 2m long skull
- estimates of jaw muscles suggest could have taken down a hadrosaur no problem (african crocs can take down zebras in comparison)
non-reptile predatory denizens of mesozoic oceans
large sharks, large predatory fish, etc.
the Cretaceous “Ginsu” shark (Cretoxyrhina mantelli)
- up to 7m long
- chunk of mososaur back sliced off by ginsu shark found
- cannot yet distinguish between hunting and scavenging by the ginsu shark
Amniotes-ammonites and nautilus chambers
ammonites and nautilus pumped gas into chambers in their shell to control buoyancy at different depths
were marine ecosystems of the Mesozoic more, less, or equally diverse to how they are today?
equally
Pterosauria
- Late Triassic - Cretaceous 100 + species.
- Wing span 0.5-12 m (most 2-4 m)
- Unique features:
1) Short trunk
2) Large head with pointed jaws and teeth
3) Wings supported by elongate 4th digit.
4) 5 long toes on foot with the 5th divergent.
5) Hollow bones.
6) Large brains w/big optic lobes, cerebellum, reduced olfactory lobes.
Pterosaur Wings
- A great example of an analogous structure built on a homologous one
- diff wings we see in vertebrates:
- all have basic forelimb plan-1 bone, 2 bone, little bone, digits
- Wings supported by 4th digit.
- Wing membrane has stiffening fibers.
- Could be folded at shoulder, elbow and wrist-like modern birds
Pterosaur Flight
-Flapping (powered) flight -not gliding flight
-Flight muscles located ventrally, as in birds
-Pterosaurs had massive flight muscles and well-braced shoulders
-Most appear to have been superb fliers
– Huge sternum, thick humerus = massive flight muscles
– Had the lightest skeleton of any vertebrate animal ever
– Had large, toughened wing
– Shoulder socket faced forward and outward as in birds, allowing great wing flexibility
-Larger pterosaurs (e.g., many pterodactyloids) probably soared more than flapped
comparison to birds
-Sternum, crests on humerus, and coracoids in pterosaurs as robust as that of birds
– Wing shape similar to those of modern soaring birds
-probably as good of (or better) flyers as birds
pterosaur vs mammal bones
- Thin-walled (~1mm thick in largest specimens), hollow bones in pterosaurs (right) compared to thick walled, marrow-filled bones in mammals (left)
- hollow bones Lightened the pterosaur skeleton, making flight easier.
The two groups of pterosaurs
- Rhamphorynchoids
- Pterodactyloids
The two groups of pterosaurs-Rhamphorynchoids:
- mid Triassic to late Jurassic
- Smaller – most >1m wingspan
- Longer tail, ogen with flange
- Small heads
- Uniform teeth
- Short necks
The two groups of pterosaurs-Pterodactyloids:
- Early Jurassic to end Cretaceous
- Larger – up to 12m wingspan, most 3-6m
- Short/no tail
- Large heads with headgear
- Few/no teeth
- Long necks
Pterosaur diet/how got food
Primarily fish eaters (just based on sharp little teeth), some insectivorous, some planctivorous?
- diversity in pterosaur feeding types
- pterosaur skimmers-possible method of catching fish, skim surface of water with beak while fly
- thalassodromeus from Cretaceous maybe did this-lower jaw tapers to a point like modern skimmers?
- scavengers?
pterosaur gastroliths?
- maybe had them
- birds use them, so why not pterosaurs?! A nice case of convergence
pterosaur crests
- diversity in crests
- reconstruct shape using fossils, guess on color-but diff colors and shapes
- crest function: display? temperature regulation?
- probably for display-there’s some evidence of sexual dimorphism
- a pterosaur bone may give us an answer-crests found in diff sizes-if changes size as species grows up/diff sizes found, evidence for sexual selection
upright posture in pterosaurs?
- not likely
- based on few known pterosaur trackways-front hands on ground, walk sort on all 4s
pterosaurs as prey
- pterosaur found in the gut of a velociraptor
- pterosaurs as part of a spinosaur diet
- rhamphorynchus caught by a fish at Solnhofen
birds
- Extant archosaurs (related to/ derived from extinct dinosaurs)
- Endothermic
- ORIGIN: Jurassic (208 - 146 MYA)
bird anatomy-skull
- loss of teeth
- enlarged brain
bird anatomy-forelimb
- carpometacarpus-fused carpals and metacarpals
- fusion of digits I-III
- loss of digits IV & V
- Furcula (“wishbone”)-fused clavicles
evolution of the wrist bone in birds
- carpals fused over time
- active research going on on this
bird anatomy-axial skeleton
- axial skeleton-large sternum with big heel/raised ridge in the middle of it (called kneeled sternum)-that’s for flight muscles
- Pygostyle-reduced and fused caudal vertebrae-start to fuse up some of the parts of their axial skeleton-fusion tends to reduce weight
- don’t have a bony tail-have a feathery tail
bird anatomy-wings
- flight muscles that lift weigh up and down on front
- pectorals
- then another muscle that goes through pulley system, little hole-attaches to other side of wing-helps bring the wing up
- these 2 muscles that help flight both on the front!!
- modern bird flight muscles-25-30% bird weight
- in modern birds, flight muscles (heavier cuz not fused?) take up a lot of weight, which is why they keep them anterior so not being dragged down-don’t want to be unstable going back and forth as fly
bird anatomy-hindlimb
- lost tarsals-fused into tibia or metatarsals
- tibiotarsus-fused tibia and tarsals
- tarsometatarsus-fused tarsals and metatarsals
- loss of digit V
- reversed digit 1 -digit 1 points backwards-allows them to perch
- reversed pubis
- synsacrum-fused sacral vertebrae and pelvis
Bird Anatomy-Feathers and Pneumatic Bones
-feathers more important and complex than we realize
fibers hold onto each other-keeps that nice smooth shape-break if try to bend other way
-pneumatic bones-bones w air spaces in them-we have this but filled w marrow-filled w ait for them-connected to their entire respiratory system-to make their breathing slightly more efficient
Bird characters in Dinosaurs
- Pneumatic bones – saurischians
- Modified foot – theropods
- 3-finger hand – theropods
- Furcula – coelurosaurs
- Pygostyle - coelurosaurs
- Enlarged tibia – maniraptorans
- Large brain – maniraptorans
- Reverse pelvis - maniraptorans
- Feathers – possibly throughout dinosaurs
Are birds dinosaurs?
Yes, they are maniraptorian dinosaurs.
(maniraptor-smallest group within dinos-includes dinoneichus-birds are in this group)
-birds=dinos has been suggested since Darwin-but really made definitive statement in Dino Renaissance-so know now birds are dinosaurs
Cretaceous collection of large-brained, agile, bird-like theropods.
- troodontids, dromeosaurids (“raptors!”), velociraptor
- Many of these lineages are small, and become smaller over time.-get smaller as get closer to birds-change in physiology that’s happening probably-as get endothermic-if too big, overheat
Archaeopteryx
- Earliest definitive bird-under debate if actually earliest bird, but close enough to be the earliest bird that we can use it as a model
- Late Jurassic – 150Ma
- Solnhofen Limestone, Germany
- 30-50 cm long
- some fossils found w/o feathers -thought this was diff species-but later realized same species-at Solnhofen it’s amazing cuz could see feather imprints, preservation so good-in the ones w/o wings feathers probably just decomposed too quickly?
Archaeopteryx compared to modern birds vs. dinos
Archaeopteryx displays a mix of traditionally avian and dinosaurian characters. Avian: 1) Feathers 2) Wishbone 3) Reverted big toe Dino: 1) Teeth 2) Bony tail 3) Vertical pubis. 4) Separate fingers w/claws 5) Less fusion in limbs.
Archaeopteryx is a nice example of
MOSAIC EVOLUTION: evolution of different characters within in a lineage at different rates, hence more as less independently of one another.
-probably evolved for different things than later used for-feathers probably not originally evolved for flight but later used to help flight
Archaeopteryx habits
Capable of powered flight. Feet modified for perching with retroverted hallux, elongate phalanges and claws, and curved claws-still had claws on front legs-strange cuz modern birds don’t have that-what were these guys still using these little claws for on the front limbs?
one example of modern bird that still has these claws (only baby)
- hoatzin (from South America)
- Juveniles are unable to fly at birth and have 2 wing claws that they use for climbing trees
- so maybe archaeopteryx using these claws to climb with forelimbs too, maybe not that good at flight yet
Archaeopteryx claws (vs. bird claws)
- modern tree-perching and climbing birds have sharply curved claws
- claw curvature in archaeopteryx is more similar to that of arboreal (tree-dwelling) birds)
- diff uses for forelimb and hindlimb claws-forelimb claws for climbing, hindlimb claws for perching
How well could Archaeopteryx fly?
-Archaeopteryx didn’t have huge heeled sternum modern birds have for flying-so maybe didn’t have particularly strong wing muscles
-but there are some other parts of skeleton that are similar to modern birds
-deltopectoral crest-so maybe better flight muscles than we may have expected
deltopectoral crest in archaeopteryx and modern birds:
-for attachment of flight muscles
-other attachment site at sternum and/or wishbone in Archaeopteryx
so, archaeopteryx may have had larger flight muscles than tiny sternum suggests
Feather asymmetry in modern flying birds and Archaeopteryx
Feather asymmetry (like airplane wings-tapers off at end) helps provide lift and so its presence suggests flight.
Evolution of Feathers
Feathers clearly derived from reptilian scales
Made of same material.
Develop in same way.
Are homologous.
-intermediate forms found in fossils and in modern birds
-prominent rachis, interlocked barbules, flat “vane”
Feathered Dinosaurs
- Feathers may have evolved multiple times in different dinosaur lineages
- Implies that feathers may not have been first evolved for flight
- wings may have evolved for display, sexual selection, thermoregulation, gliding-evolved separately and not for powered flight-but eventually evolved into that
- some sort of feathers may have been present in many dinosaurs
- in some ways seem like dinos almost prime for dinos
microraptor
2 sets of wings-gave stability-not powered flight, glided
Theropod feathers
- Note theropod feathers are symmetrical (similar to non-flight feathers in birds).
- So feathers not originally for flight.
- Feathers likely evolved initially for heat regulation and/or display for mating.
- maybe dinos had feathers at 1 stage of life but not others-like young had feathers then lost them-think happened w T-Rex babies
dinosaur/feather colors!
- usually can only look at shape-but recent research helps tell us color
- -melanosomes in the integumentary filaments of the dino Sinosauropteryx
- some theropods may have had iridescent feathers-microrapter gui
- makes sense that dinos more colorful than we thought in the past
- not just lizard colors-more like birds-get more colorful reconstructions now because we know this
- don’t always know exact colors of each dino but getting better at it
- Due to abundance in color in many species of closest living relative to dinosaurs: birds
The homology of all these structures (feathers in birds & theropods, filament structures in some ornithischians, etc.) is….(clear/unclear)
very unclear, and so it is probably best not to use feathers as a key character in arguing bird origins.
Now know more about transition from theropod to bird
-Maniraptor theropods were pre-adapted for evolution of flight
How were Maniraptor theropods pre-adapted for evolution of flight?
they. ..
- had feathers
- were bipedal
- were small (some of them!)
- had hollowed bones and enlarged spaces in skull
- had long, flexible arms and hands
- so they were kind of ready to fly-had adaptations to flight similar to modern birds, even if not originally evolved for flight-had a lot of characters that we associate with flight in birds, but were using them for something else
- did birds learn to fly by running from the ground and developing better and better flight muscles to fly off ground?
- or from gliding down from trees first
-ground up hypothesis
-Trees Down Hypothesis
FALSE DICHOTOMY
-New evidence suggest both are partially right.
-used wings to help them run well/run uphill, and run up trees, eventually led to flight
ground up hypothesis
Birds evolved from theropods that were terrestrial cursors and wings evolved to assist in insect catching. Primary evidence : no theropods could climb.
Trees Down Hypothesis
Birds evolved from theropods that climbed to avoid predation and forage, and gliding wings evolved for movement between trees. All early birds are arboreal. It is unlikely that wings would evolve in purely terrestrial animals.
ground up hypothesis-new evidence for
-New evidence of arboreal theropods based on hand and foot anatomy. Dromeosaurids such as Bambiraptor, Deinonychus, and Microraptor could probably use their curved claws for climbing.
Trees Down Hypothesis-new evidence for
-New evidence from the study of extant ground birds that demonstrates the advantage of small wings for tree climbing
Wing-Assisted Inclined Running (WAIR) hypothesis for the origin of flight.
- “Incipient feathered forelimbs of proto-birds provided the same locomotor advantages for inclined running as are present in extant birds.” (Dial 2003)
- The big advantage : improved hindlimb traction for ascent .
- WAIR is an intermediate stage allowing arboreality, and leading to the evolution of more sophisticated flight.
- this is a good middle ground between the dichotomies-used wings to help them climb trees-intermediate stage between no wings/wings not really used for anything to do with movement/flight and wings used for flight
Maniraptorans as young modern birds
-Modern juvenile birds can’t fly, but they do use their wings.
Origin of powered flight in birds
- May have been for escape
- Earliest birds probably fed on ground or in trees (weren’t good enough at flying yet to catch insects “on the wing”)
- Early birds could run away and jump/scramble into trees, glide down to a safer location in order to escape predators
Another possible use for wings
-Killing behavior – Used for stability while grasping prey with enlarged claws-and to hold down prey?
Gliding in other theropods
-Microraptor gui
The road to modern birds…
-“Feathered” maniraptoran dinosaurs (Cretaceous)
-Archaeopteryx (Jurassic)
-Basal bird taxa (all Cretaceous)
Confusciusornis
Sapeornis
Jeholornis
Rahonavis
-Enantiornithines (Cretaceous). 40+ species.
-Ornithurae (early Cretaceous-Recent), 9000 living species.
Evolutionary trend in the earliest birds :
-From a less arboreal foot and a climbing hand (e.g., Archaeopteryx) to a more arboreal foot and a flying hand (e.g., Sinornis).
BASAL BIRDS
-Body size : large crow to sea bird
-Advanced characters: no teeth, horny beak, synsacrum, pygostyle, fully reversed hallux, long tail feathers.
-Primitive characters : wing retains claws, relatively short wings, hindlimb structure.
Confuciusornis, Early Cretaceous, 125 ma, China:
ENANTIORNITHINES : the opposite or other birds
Almost all were perching birds (long toes, curved claws), but at least one may have been a wader.
First recognized in 1981 based on metatarsal features. Now defined by suite of shared derived characters
ORNITHURINES
- Much less common in the early Cretaceous than entantornithines, but the only birds to survive the KT boundary.
- Many early taxa show adaptations for living in or near water
- Includes all modern birds
- Advanced in having:
1) Keeled sternum,
2) Strut-like coracoid,
3) Short pygostyle,
4) Completely fused carpometacarpus. - Primitive in having:
1) Teeth (for fish eatong)
2) 2 claws on wing
bird diversity over time
-increased over time, birds spread quickly
paleognathae
- mostly flightless birds
- moas, paracathartes, lithornis, palaeotis, casuarius
- emus, kiwis, rheas, ostriches
- oldest fossils are from the paleocene and eocene of Europe and NA. Extant forms, tinamous and ratites, only go back to the Miocene.
- restricted to southern continents for biogeographic reasons-Gondawanaland
- Cretaceous
- giant flightless birds that fill this predator niche for a while until get giant mammalian predators, then these birds start to go extinct
early Cenozoic terror birds
- Diatryma, NA and Eur.
- closest sister taxa=ducks & fowl
- Phorusrhacid birds: Europe, SA, NA.
- there were some giant flying predators as well-like this giant hawk that was adapted to eat big flightless birds-went extinct when humans came to Madagascar
- ex: Harpagornis
- there were some giant flying predators as well-like this giant hawk that was adapted to eat big flightless birds-went extinct when humans came to Madagascar-ex: Teratornis
the other kind of vertebrates that evolved flight:
- bats-but do it differently-evolve to have this leathery wing-holds 4 fingers-the fossil record of bats and transition to bats is awful, compared to transition to birds which has great fossil record, lots of fossils found
- wings originating independently have different skeletal structures, revealing tehir convergent evolution
- long middle finger holding up wing-but 4 fingers in all, support wing
- fossil record of bat is pretty bad-don’t have good documentation of transition to bats/flight
- makes sense-they’re small, don’t tend to live in places where fossilize well when die there
J.John “Jack” Sepkoski - University of Chicago
-First to look at large- scale trends in marine communities across time
-produced graph showing:
What does it show?
-First, is increasing diversity over the entire Phanerozoic
-Reasons for this increasing diversity:
– Pull of the recent
– Ecological diversification
Reasons for this increasing diversity: Pull of the Recent
- Artifactual - sampling and interest bias
- Small part of a much larger problem with paleontology - TAPHONOMY
Reasons for this increasing diversity: Ecological Diversification
- Positive feedback - diversity begets diversity – Creation of ‘ ecospace ’
- e.g. tiering within the marine community
- Also predator-prey interactions - “escalation” (Vermeij)
- so this says that the diversification was real (not result of just more discovered later)
Back to the graph…
times when variation drops dramatically
-these are extinction events
-EXTINCTION: 5 major ones:
-End Ordivician
-End Devonian
-End Permian **
-The mother of them all - 90% of all species wiped out
-End Triassic
-End Cretaceous - K/T **
(**=gonna concentrate on these)
changes in variation/extinctions when period change because…
- defined end of mesozioc as end of a bunch of species, beginning of a new one-why tend to happen at these boundaries-because we defined boundaries (eras, periods) based on the change in species, diversity at the time, extinction of species, appearance of a new species
- so it’s not a coincidence that extinctions happen at these boundaries-they’re how we defined them
Mass Extinctions defined by
– Being global in extent
– Affecting marine and terrestrial organisms
– Being brief in duration
Mass Extinctions caused by
– Major climatic change – Sea level changes – Volcanism – Plate Tectonics – Extraterrestrial (meteors, things that come from outside of the earth and affect earth)
The End-Permian (P/T) Extinction
-The Paleozoic Era ends with a mass extinction event
-Possible Causes
– Formation of Pangaea
– Marine anoxia: Oxygen levels greatly depleted in oceans (no mixing!)-not same currents as before, not as much mixing of surface water and deep waters, deep waters become anoxic, depleted of oxygen
– Sea level falls about 100 meters-probably related to the formation of pangea
– Volcanic activity: huge basalt flow in Siberia about 251 Ma
-probably a bit of all of these causes-not just 1
the earth 251 mya
- Pangea
- location of fossil deposits that include the PT boundary
late permian diversity
- seas teaming with life
- the land was equally diverse
Who died in the P/T extinction?
-49% of all marine families
-63% of all terrestrial families
surviving families squeaked through at low diversity
-this can be used to estimate that 80-90% of all marine species were lost
Bioturbation
the disturbance of sedimentary deposits by living organisms. For example, worm burrows
-see that Permian and Triassic sediment different-less living organisms-proof of the extintion event
How fast did the P/T extinction happen?
- In the marine realm, very fast. In less than 1 million years, about 94 % of the species disappear from this well-studied fossil deposit in China.
- maybe many small extinctions around this time that contributed to it, even a little after it continued
Isotopic evidence suggests…
- environmental turmoil
1. Oxygen ratios (18O: 16O) indicate an approximate 6oC rise in global temperatures.
2. Carbon isotope ratios reveal a dramatic increase in atmospheric and oceanic 12C levels, suggesting a serious decline in plant productivity.-one of the reasons behind this is that plants tend to use lighter isotopes-basically most carbon is c12, then a little bit of c13- plants tend to use more c12-so if sudden increase in c12, means plants no longer using up that lighter carbon, getting released to environment-suggests there was a big biotic crisis, that a lot of plants died - In nature, most carbon exists as 12C with minor, but detectable amounts of 13C. Ratio of 13C:12C is the same in the oceans and atmosphere. During photosynthesis, plants (including algae) preferentially utilize 12C thus removing it from the ocean-atmosphere system. When they die, burial will continue to sequester the 12C. Consequently, during times of high plant and animal productivity, the 13C:12C ratio will increase. So, the increase in 12C at the PTR boundary suggest a major biotic crisis occurred.
what caused the mass P/T extinction?
a) Bolide impact?
b) lots of volcanism?
c) marine regression?
- methane hydrates
- there’s also evidence of a drought at the permian boundary and
- runaway greenhouse earth
- probably multiple causes
What could account for global warming and the increase in 12C?
- Bolide? Doubtful and there is no definitive evidence yet for a bolide impact at or near the PTR boundary.
- Marine regression? Unlikely. Also, it does not explain terrestrial extinctions and the rapidity of the extinctions.
- Volcanism : maybe.
marine regression
- Marine regression (drop in sea level) would remove extensive areas of shallow nearshore environments. (most diversity occurs close to shore)
- Less area means increased competition and species extinctions.
The Siberian Traps
- Largest known volcanic eruption.
- 2 million km2 of basalt that today cover 1.6 km2 of eastern Russia to a depth of 400-3000 meters.
- The eruptions occurred over a span of one million years and have been dated at 251 ma
- The Siberian traps are flood basalts:
- Flood basalts are thought to result from plumes that rise within the mantle and emerge on the surface in fissures, creating successive layers of lava.
- Basically HUGE hot spots!!! that’s burning hole in continental crust-get huge fields of basalt deposited at that time as stuff from the mantle comes up to the surface and spreads out on surface
- so could have caused the extinction-evidence that volcanos caused it/for the extinction in general
But how did that (the volcanos) affect life?
- Volcanic eruptions produce: ash, CO2, sulfur dioxide, water vapor, and various other gases
- this can contribute to global warming, ozone destruction, acid rain, and global cooling
- quick cooling (100-1000 years) then warming of the earth-global warming for (1mil years)
- So, the Siberian traps probably had a major impact on the earth’s climate and could explain the global warming.
- But can they account for the large increase in 12C?
- Models say no. Not even in combination with the instantaneous destruction of all life on earth.
- so we need another explanation
Another possibility that could’ve caused the extinction-methane hydrates
The melting of methane hydrates (combination of ice and methane).
- Methane hydrates are cages of water molecules that surround and trap methane molecules. They freeze under moderate pressures (e.g. > 300 meters below sea level) at temperatures above the freezing point of water.
- Global warming could raise sea temperature enough such that these methane hydrates would melt, releasing methane into the water column.
- Methane (CH4) will rapidly react with O2 to form CO2 and H2O.
- The CO2 will rise to the surface as bubbles and evaporate, raising CO2 levels in the atmosphere.
- feedback cycle where gets worse and worse as global warming continues, methane released more, which contributes to more global warming
- A runaway release of gas could occur if marine methane hydrates melted and this may be what happened at the PTR boundary.
- In the ocean, the release of CO2 also shifts the pH of the water, making it more acidic, and causes calcium carbonate to dissolve, thereby killing a wide variety of marine organisms (corals, all shelled creatures).
A runaway greenhouse earth?
- could’ve contributed to the P/T extinction
- massive greenhouse earth led to massive volcanic eruptions, which leads to atmospheric CO2 increase, which leads to global warming on land and sea, which leads to melting of methane hydrates, which leads back to atmospheric CO2 increase, go through cycle again
- we worry this will happen to us now, because we have global warming, and methane deposits
Recovery from the PTR extinction
- slow
- Marine biodiversity at the family level did not reach pre-Triassic levels for 100 myr. Complex ecological structure returned to the oceans within 10 myr.
- there’s evidence of oxygen-poor water 244 mya
- data on the recovery of land are sparse, but new groups replace formerly dominant forms
Recovery from mass extinctions
-Is there a lag in diversity recovery?
-How are communities rebuilt?
– First back are the low diversity, high abundance, quickly reproducing faunas - “weeds”
-Are the most complex forms hit the hardest? (we learned that earlier-as species evolve to be more complex and bigger, more susceptible to extinction)
-Importance of refugia - “Lazarus taxa”-species migrate to places where climate change not as bad (where no fossil record available), then come back later-so see them reappear in fossil record
who survived the P/T extinction?
- a few marine reptiles, few dinos (who become birds), and pterosaurs make it out
- bees, lizards, snakes, marine species all hit hard, but do make it through
Bolide impact-meteor theory
Extraterrestrial Impact!-first proposed in 1980 by Luis Alvarez and colleagues-meteor came to earth, killed most dinos
evidence for bolide impact
-Iridium is not very common on earth-common in meteors and things from space
-so see this huge spike at K/T boundary-so this is their main line of evidence for a meteor causing the K/T extinction
-then looked and found them all over the world
-looked for more evidence-wanted to find a crater-and they did-dated it, looked to be right age
-Chicxulub Crater was discovered in 1990. 195 km in diameter.
-In addition, it was near sediments that indicated a tsunami occurred about the same time, and had lots of glass spherules (droplets of melted earth, pushed up?, solidified in atmosphere, landed on earth) and shocked quartz (only gets formed in high pressure-that you would see formed in an impact)
-Fluvial sediments show increased acidity, and there is evidence of global fires
-think they may have found a piece of the meteorite too
-meteor would’ve set atmosphere on fire-and we have evidence of many forest fires at the time
-also would’ve caused tsunamis-we have evidence that there were tsunamis
-so looks like this meteor did happen
BUT, DID IT KILL THE DINOSAURS?
-maybe it wasn’t the impact of the meteor, but other things that contributed to it
-also a volcanic event that happened at the time-Deccan traps
Consequences of a Bolide Impact
1) Dust, smoke, and debris that blocked sunlight for many months; and
2) An instantaneous pulse of thermal energy that ignited many fires
- photosynthesis basically stopped at the time
- rise in iridium contributes to decline in pollen
Plants change across the K/T
-Plants swithch to “weedier” fast growth strategies
A paradigm shift in science -uniformitarianism vs catastrophism
- Previously, historical scientists (paleontologists, geologists, etc.) followed a fairly strict uniformitarian stance – the processes happening now were the same in the past.
- Catastrophism was associated with deluvian (flood) ideas.
- Now we have a Neo-Catastrophist/ Uniformitarian view – allows for unique events in the past (and future)
- it’s kind of a combination of the 2 views-uniformitarian but sometimes there are catastrophes
Deccan Traps
- Indian basalt flows, similar to the Siberian Traps associated with the P/Tr boundary
- 2000m thick in some places
- Dated to 68.5-66.5Ma
- May have contributed to the decline in diversity at K/T boundary
another idea about meteor/effect on dino extinction
- The bolide impact was the final blow that eliminated dinosaurs, pterosaurs, and others, but all these groups were already in decline due to climate change, sea level fall, and volcanic activity.
- There is some evidence that large herbivores were on the decline, which may have made communities more susceptible to large scale changes
- but some say that not going extinct before-rapid extinction
- signor-lipps effect: since dinos fossilized so rarely, (large dinos) may look like they’re going extinct before they’re actually going extinct-small ones preserved more readily-unlikely to find big dino preserved right at k/t boundary just because not found often but could’ve existed then
- so, yes, there may have been some decline going on at the time, but probably not much
- so recent research support rapid extinction
the end of the dinos was the beginning of
the “Age of Mammals” (and Birds)
fossils
-Evidence of past life, including body, chemical, and trace fossils.
-Includes:
– Whole Body Fossils
– Preservation of Hard Parts & Petrification
– Molds and Casts
– Trace fossils – ichnofossils (ichnology)
– Chemical traces
Diagenesis
the physical and chemical processes that lead to fossilization
Whole Body Fossils
-Mummification, frozen & bog specimens, amber
hard part preservation
either:
- fill up the spaces in the fossil with some mineral
- petrification-turn actual substance of species into some rock
casts and molds
-so can make casts and molds from these fossils, preserved as one or the other, but can make the other from it if want to see
trackways example-what animal they found trackways of and what they could tell from trackways
-footprints preserved-shoes another animal walked across their path-can tell 1 smaller than another-so probably a pack of female elephants-then a male followed behind-can tell this just by looking at trackways
Taphonomy
The study of the processes by which animals become fossilized
- composition and decomposition
- exposure and weathering
- transport and burial
- fossilization and exhumation
- how well they’re preserved has to do with how fast water flowing, how much exposed, how much energy in environment
Lagerstätte
- fossil localities with exceptional preservation
- ex: Burgess shale, Solnhofen limestone, Messel Pit, La Brea Tar Pits
Ranco La Brea
- modern day LA
- Pleistocene - 4-44 thousand years ago (kya)
- Over 4 million plant and animal fossils
- More than 600 species
- Tar pits acted as a natural trap for large animals
- Now the specimens are ‘sub-fossils’, with some of the original material still present-been permeated with asphalt so very dark-could technically get DNA out of them but chemicals you would have to use to get the tar out would get rid of the DNA
- in 1914, oil wells filled this entire area-people came to get the oil out-attracted a lot of people, made money off of it
are there dinosaurs in the La Brea Tar Pits?
no!!
instead, there are: direwolves, lions, bear, bison, horses, camels, sabertooth tiger
Los Angeles in the Pleistocene
- Broad plains, crisscrossed by rivers from the nearby mountains
- Petroleum seeps forming sticky asphalt on the surface, which get covered in water, leaves, & sediment
- basic landscape the same as now-not much plate movement
- oil forms close to the surface sediment-comes out on the surface-instead of being below rock like it usually is-more oil here than anywhere else-why LA is here-densest oil in the world, not widespread but dense
PIT 91 Excavation
(prof’s research)
- first looked at and took big fossils out to display but didn’t do much research
- Reopened in 1969
- 28’ by 28’ square divided into a 3’ by 3’ grid
- 6” thick blocks
- Extensive data capture on over 18,000 specimens
Distribution of bones in Pit 91
-Bones are clumped together in the pit
-Dating shows episodic capture in the pits
– Entrapment rates were about 1 every 50-70yrs, during entrapment episodes
-Dates mostly follow Law of Superposition (older things under younger things), although there has been some ‘mixing’
-Further proof of this ‘mixing’ is that few of the specimens are ar;culated – you rarely find skeletons that are put together
-What causes this mixing?
– Mixing of multiple deposits?
– Movement in the deposit? gooey enough that things could move around within
– Trampling? did they stay at the surface level and get trampled?
what happened to the carcasses in Pit 91 after the animals died?
not sure-scavenged, buried? already talked about this
The Tar Pit fossils have ______ food web distribution (and what does this mean?)
- have an inverted food web distribution
- a few prey get captured, many predators come to eat them, killed in trap-so predators more likely to die for once-1 prey can be responsible for the death of many predators
what happened at Pit 91 during the time of the dinos?
- Herbivores, mainly juveniles, get trapped in the tar
- This attracted carnivores, many of which got trapped themselves
- Carnivores that didn’t get trapped dragged off half of the carcasses
- What was led was quickly buried, with little weathering or abrasion
- After burial, fossils were compacted and some mixing occurred
Unanswered Questions about Pit 91
-Why do we find SOME articulated skeletons?
-How long does it take for the skeletons to fall apart in the tar?
-What causes the mixing?
– Trampling?
– Settling?
– Churning?
A start at answering how long it takes for carcasses to rot in the tar
- A controlled experiment on carcass decomposition in an actual tar pit-not much evidence for this (prof did this)
- got down to bones relatively quickly-why? what does this mean? more research should be done
Taphonomy
-Allows us to tell the story of the fossils, from the death of the animal until they were discovered
-Based on the study of modern day processes
-This can give us insights into
– the behavior of the animals
– the environment they lived in
– the geology of the area
An overview of mammal evolution: Main concepts
- Mammals are modified reptiles evolved to be endotherms via the concerted evolution of various adaptations
- Convergence to repeated forms in different taxonomic groups
- Different groups have fossil records of varying quality
- Ecological community structure can drive evolution
What is a mammal? major groups:
Three major modern groups :
- Monotremes
- Marsupials
- Placentals
What is a mammal? Obvious shared characteristics (shared-derived synapomorphies):
- Hair
- Warm-blooded, endotherm, homeothermic
- Mammary glands
- Live birth (except Monotremes)
- but none of these fossilize well-need way to describe mammals when it comes to fossils
monotremes
- popular in mesothermic-only a few alive today-in Australia
- platypus
Opossum
- dominant mammal in Australia-exist in South America too
- found in Virginia, but much more diverse in other parts of the world
- have pouch-young born very very small-grow inside the pouch
placental mammals
- anything you think of as a mammal-bats, whales, etc. (and all the ones seen below, in La Brea Tar Pits)
- and some cool carnivores
- and humans
What about fossil mammals? All the characters we’ve talked about don’t fossilize, so how do we tell we have a mammal in the fossil record?
- We have to look at their skeletons, specifically, the main character we look for is a lower jaw made of one bone
- New jaw joint evolved between dentary bone (lower jaw or mandible) and squamosal bone (on skull)
- good fossil record for this
- made our jaw stronger-more powerful bites-helped us chew
- also helped our hearing-reptiles can’t hear well-we can because of way jaws work
In the evolution of the mammalian middle ear and jaw joint:
Quadrate => Incus
Articular => Malleus
Haeckel
- “ontogeny recapitulates phylogeny”
- said development stages of species reflect its different earlier evolutionary forms-this is kinda true, especially here
- bone out then retreat back into ears-see this transition happen in the development of mammals
outer ear
tympanic membrane to outside
middle ear
air-filled chamber between the tympanic membrane and inner ear that contains the ossicles
inner ear
organs of hearing and balance + equilibrium
job of these bones/structures inside ears:
- to take air vibrations and turn them into fluid vibrations
- this ear chamber here is an air dome, connects to back of throat-auditory tube-why ears pop, or can’t hear during cold-yawm or chew, open up tube and ease up pressure there
Why did this jaw transition happen?
-It probably has to do with a suite of adaptations
– Better hearing-secondarily
– Better tooth occlusion for bear chewing-stronger bite
– More powerful bites-
– Suckling-generate more pressure(?) in mouth for sucking
-Most of these things probably had to do with endothermy
Endothermy
-The ability to keep a constant body temperature (unlike reptiles and other lower vertebrates)
-Can be active all the time BUT
– Leads to increased food requirements, which leads to the need for…
-Better food processing, i.e. chewing
– Chewing increases rate of digestion and therefore the amount of food that can be eaten per unit time
One the adaptations for better chewing is…
MAMMALS ARE DIPHYODONT : they have only two sets of teeth, juvenile and adult. (we’ve talked about this)
this diphyodonty allows for….
…precise OCCLUSION (the bringing of opposing surfaces of the teeth of the two jaws into contact, i.e. when lower teeth meet upper teeth as the mouth is closed)
Most reptile teeth are…
- single rooted
- continuously replaced, and
- simple pegs that do not occlude precisely
- so reptiles don’t chew
ENDOTHERMY =>
INCREASED FOOD NEEDS => BETTER CHEWING=> PRECISE OCCLUSION => DIPHYODONTY
In addition, diphyodonty requires….
…a period of dependency on mom for food, i.e. lactation-since adult teeth haven’t come in as well, can’t chew well-having baby teeth led to having to get food some other easier way-may have led to lactation
Endotherms need more oxygen, as well as food, so strangely enough, ____ can play into this too:
- posture
- endotherms have a more erect posture-relates to us being able to breathe better-can time breathing to running (if walk on all 4s-humans/bipedal creatures are diff)
reptile posture
sprawling
crocodilian, early MLR posture
semi-erect
mammals, dino posture
erect
Erect gait allows for…
…mammals to couple breathing and strides
turbinates
Mammals also have unique structures in their nose, the turbinates that make their breathing more efficient.
FUNCTION OF TURBINATES :
1) CONDITION INCOMING AIR
2) CONSERVE HEAT
3) CONSERVE WATER
Because: HIGH VENTILATION RATES* IN ENDOTHERMS CREATE A WATER and HEAT CONSERVATION PROBLEM
*Ventilation rate = breaths/minute
Early evolution of mammals is a story of linked adaptations:
endothermy: -leads to fur and hair
- also leads to needing more food/oxygen
- which leads to needing a stronger bite
- leads to new jaw joint
- new ear
- better locomotor abilities
- leads to erect posture
- better chewing
- diphyodonty
- lactation
- precise occlusion
- more efficient breathing
- turbinates
stem reptiles
- 1 group leads to dinos, but 1 to mammals
- all of these are amniotes-all derived from this egg-laying amniote-free from water, laid eggs on land
mammal-like reptiles
- pelycosaurs
- therapsids
- cynodonts
Pelycosaurs
- the earliest mammal-like reptiles
- many were carnivorous
what P/T extinction means for these mammal-like reptiles
giant extinction event, pelycosaurs die out, 1 therapsid group survives (but others die), cynodonts survive and thrive, then mammalia thrives-the others dying out leaves room in niche for mammals
therapisds
- mammal like reptiles-filled main predator niche
- ugly
- carnivores and herbivores
- herbivore ex: lystrosaurus-important biogeographic indicator that Wegner used in his theory of continental drift-cuz found in Africa-strange
- first evidence of respiratory turbinates
- starting to look a bit more mammalian, at least in their physiology
cyodonts
- really starting to look like modern mammals
- looks like weird mix between tiger and lizard
- nice transitional group from reptilian looking things to modern mammals
earliest known mammal
- 220 mya-Triassic
- earliest true mammals that are completely endothermic-they were small-true for dinos too-earliest lineages that lead to birds are small-see this in mammals too
- shrew-like
mesozoic mammals
- originally thought possum, shrew-like things, and none larger than a house cat
- new research suggests they were more diverse than previously thought, and some bigger than thought
- so turns out much more diverse in mesozoic than earlier thought-look more like pictures above-not just little rat-like things running under dino feet
- 1 even found w dinosaur remains in stomach
- warthog size-bigger
when dinos die out….
mammals diversify and turn into all the diff groups we see today-really come into their own after dinos die out
when look at placental mammals and australian marsupials…
a lot of evidence of convergence-similar stuff back then to what see today-filled all the niches that would expect them to fill, that normal, placental mammals fill
why do we see such convergence with marsupials and placental mammals?
has to do with plate tectonics-when marsupials evolved, continents all together, then split apart, marsupials get stuck in australia on our, start to fill niches there-so cause of this convergence we see is because of plate tectonics
General Mammal Summary
- Living Mammals belong to 3 groups
- Fossil mammals can be distinguished by their skeletal structure, mainly their jaws and ears
- Mammals are evolved from reptiles, and have a number of linked adaptations that allow them to be endothermic
- Mammals were around during the reign of the dinosaurs, but many (not all) were small and innocuous.
- Mammals radiate (diversify) after dinosaurs disappear
- Marsupials show many convergences with placental mammals, due to their being isolated from them and filling the same ecological niches (plate tectonics)
In most ecosystems there are far more carnivores than herbivores.
Select one:
a. True
b. False
b. False
Dinosaurs probably had a 4-chambered heart.
Select one:
a. True
b. False
a. True
An animal generates its body heat internally using metabolic waste heat. It is said to be a(n): Select one: a. gigantotherm. b. ectotherm. c. endotherm. d. homeotherm. e. poikilotherm
c. endotherm
A large animal tends to keep a relatively constant body temperature without generating any heat internally is said to be a(n): Select one: a. endotherm. b. homeotherm. c. gigantotherm. d. poikilotherm. e. ectotherm.
c. gigantotherm.
Which of the following is NOT an adaptation for eating plants that is found in dinosaurs? Select one: a. gut fermentation b. gastroliths c. dental batteries d. hypsodonty e. predentary bone
d. hypsodonty
What does it mean when we say theropods were “airheads”?
Select one:
a. Their skulls were filled with air sacs.
b. They had small brains.
c. They had projections on their skulls.
d. They flew and had feathers like birds
a. Their skulls were filled with air sacs.
Which of the following groups of theropods were known for their "headgear"? Select one: a. therizinosaurs b. coelosaurs c. ornithomimids d. ceratosaurs e. coelophysids
d. ceratosaurs
Pneumatization in theropods is analogous to what in humans? Select one: a. Chewing b. Walking on "tip-toes" c. Appendix d. Sinuses
d. Sinuses
Which of the following does NOT belong in tetanurans? Select one: a. therizinosaurs b. spinosaurs c. ornithomimids d. coelosaurs e. ceratosaurs
e. ceratosaurs
Which of the following belongs in maniraptors? Select one: a. ceratosaurs b. abelisaurs c. tyrannosaurs d. deinonychosaurs e. allosaurs
d. deinonychosaurs
Dioecious means that there are male and female plants.
Select one:
a. False
b. True
b. True
Pneumatization in sauropod vertebrae:
Select one:
a. means they were filled with air spaces.
b. allowed them to lift their neck vertically.
c. was an adaptation associated with their small heads.
d. means they had a powerful neck ligament.
a. means they were filled with air spaces.
Which of the following taxa probably had thin, pencil-like teeth restricted to the anterior end of the jaw? Select one: a. titanosaurs b. diplodocids c. brachiosaurs d. prosauropods e. camarasaurids
b. diplodocids
Which of the following plant taxa needs water to germinate? Select one: a. angiosperms b. conifers c. pteridophytes d. cycads e. ginkgos
c. pteridophytes
Which of the following is NOT a line of evidence that the frills and horns of ceratopsians were for sexually selection purposes?
Select one:
a. the fact that only adults had them
b. the presence of battle scars on the faces of some ceratopsians
c. the sexual dimporhism of the frills
d. the fact that all species of ceratopsians had some form of them
d. the fact that all species of ceratopsians had some form of them
Which of these is probably the most primitive thyreophoran? Select one: a. Ankylosaurus b. Scelidosaurus c. Nodosaurus d. Scutellosaurus e. Stegosaurus
d. Scutellosaurus
Which of the following was probably an adaptation for better locomotion despite armored skins in ankylosaurs? Select one: a. the presence of a cingulum b. a synsacrum c. armor covering cranial sutures d. a broad skull e. post-orbital processes
b. a synsacrum
Which of the following is a characteristic the defines ornithischians? Select one: a. body armor b. feathers c. lizard hip d. heterodont dentition e. predentary bone
e. predentary bone
Marginocephalians are said to be endemic, which means:
Select one:
a. they are only found in specifc time periods.
b. they have specialized dentitions fo herbivory.
c. they have a restricted geographic distribution.
d. they have many structures related to sexual selection.
c. they have a restricted geographic distribution.
Some ankylosaurs had pneumatized skulls.
Select one:
a. True
b. False
a. True
Most non-amniotes: Select one: a. have divided cloacas b. have hemipenes c. possess various cloacal protuberances d. have external fertilization e. develop eggs internally
d. have external fertilization
Which of the following is NOT an adaptation to herbivory seen in ornithopods? Select one: a. gastroliths b. dental batteries c. cranial kinesis d. duck-bill e. jaw joint below the tooth row
a. gastroliths
Most insects lay lots of eggs and don't take care of the young. We would say they are: Select one: a. r-selected b. sexual selected c. k-selected d. naturally selected
a. r-selected
The best reason to live in herds or flocks is:
Select one:
a. safety
b. having lots of mates
c. you can all eat together
d. you can beat other groups to resources
a. safety
Ornithopods only walked bipedally.
Select one:
a. FALSE
b. TRUE
a. FALSE
The best place to see exposures of the Cretaceous Kaiparowits formation is:
Select one:
a. Solnhofen, Germany,
b. Petrified Forest National Monument.
c. Cleveland-Lloyd Dinosaur Quarry,
d. Grand Staircase-Escalante National Monument.
e. Dinosaur National Monument.
d. Grand Staircase-Escalante National Monument.
A great place to see exposures of the Jurassic Morrison formation is:
Select one:
a. Solnhofen, Germany.
b. Petrified Forest National Monument.
c. Grand Staircase-Escalante National Monument.
d. Dinosaur National Monument.
e. Dinosaur Provincial Park, Alberta.
d. Dinosaur National Monument.
The major carnivorous group just before the dinosaurs was: Select one: a. therapsids b. mammals c. huge amphibians d. other (non-dinosaur) archosaurs
d. other (non-dinosaur) archosaurs
Many early crocodile-like reptiles were bipedal.
Select one:
a. True
b. False
a. True
The Colorado Plateau extends to all the following states, EXCEPT: Select one: a. Wyoming b. New Mexico c. Colorado d. Utah e. Arizona
a. Wyoming
This is the group that many Mesozoic marine reptiles belong to. Select one: a. synapsids b. anapsids c. euryapsids
c. euryapsids
Which of the following taxa had hands and feet most modified into paddles? Select one: a. Plesiosaurs b. Placodonts c. Ammonites d. Nothosaurs
a. Plesiosaurs
Pterosaurs support their wing mainly with: Select one: a. 4 elongate digits on their hand. b. with feathers. c. an elongate 4th digit. d. their entire arm.
c. an elongate 4th digit.
Which of the following is NOT a group that birds belong to? Select one: a. maniraptorans b. dinosaurs c. tetanurans d. coelophysids e. ceolurosaurs
d. coelophysids
The most common diet of pterosaurs was: Select one: a. dinosaurs. b. fish. c. plankton. d. other pterosaurs.
b. fish.
Which of the following adaptations to flight do pterosaurs share with birds?
Select one:
a. a wing supported by an elongate 4th digit
b. a wing supported by their entire arm
c. feathers
d. hollow bones
d. hollow bones
Which of the following taxa did NOT have members that had feathers? Select one: a. tyrannosaurids b. ornithomimids c. sauropods d. dinosaurs e. maniraptorans
c. sauropods
Ornithurines includes modern birds.
Select one:
a. False
b. True
b. True
Maniraptoran theropods had all the following characteristics of birds EXCEPT: Select one: a. small size b. bipedality c. hollow bones d. keeled sterna e. feathers
d. keeled sterna
Over time, birds emphasized their feet for climbing trees.
Select one:
a. True
b. False
a. True
who made me add a 600th card just to appease their craziness (I’m an enabler now)?
Lex
